System and method that provides efficiency and flexiblity in inductive charging

ABSTRACT

A system and method for improved efficiency and flexibility in inductive charging. In accordance with an embodiment, the system comprises a base unit having one or more primary coils, wherein each primary coil is configured so that when a current is passed through it, a magnetic field is generated in a direction substantially perpendicular to the plane of the primary coil; one or more secondary coils or receivers associated with one or more mobile device; and one or more components within the base unit and/or the mobile device, for improving efficiency and/or flexibility in inductive charging. When the one or more mobile device is placed in proximity to the base unit, the perpendicular magnetic field is used to inductively generate a current in the one or more secondary coils or receivers associated therewith, to charge or power the device.

CLAIM OF PRIORITY AND CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/708,548, titled “EFFICIENCY AND FLEXIBILITY IN INDUCTIVE CHARGING”,filed Dec. 7, 2012, which is now U.S. Pat. No. 8,947,047, issued on Feb.3, 2015; which application is a continuation of U.S. patent applicationSer. No. 13/442,698, titled “SYSTEM AND METHOD FOR INDUCTIVE CHARGING OFPORTABLE DEVICES”, filed Apr. 9, 2012, which is now U.S. Pat. No.8,629,654, issued Jan. 14, 2014; which is a continuation of U.S. patentapplication Ser. No. 12/116,876, titled “SYSTEM AND METHOD FOR INDUCTIVECHARGING OF PORTABLE DEVICES”, filed May 7, 2008, which is now U.S. Pat.No. 8,169,185, issued May 1, 2012; which application is acontinuation-in-part of U.S. patent application Ser. No. 11/669,113,titled “INDUCTIVE POWER SOURCE AND CHARGING SYSTEM”, filed Jan. 30,2007, which is now U.S. Pat. No. 7,952,322, issued May 31, 2011; whichclaims the benefit of priority to U.S. Provisional Patent ApplicationNo. 60/763,816, titled “PORTABLE INDUCTIVE POWER SOURCE”, filed Jan. 31,2006; U.S. Provisional Patent Application No. 60/810,262, titled “MOBILEDEVICE, CHARGER, AND POWER SUPPLY”, filed Jun. 1, 2006; U.S. ProvisionalPatent Application No. 60/810,298, titled “MOBILE DEVICE, BATTERY,CHARGING SYSTEM, AND POWER SUPPLY”, filed Jun. 1, 2006; and U.S.Provisional Patent Application No. 60/868,674, titled “SYSTEM FORPROVIDING A PORTABLE INDUCTIVE POWER SOURCE”, filed Dec. 5, 2006; whichapplication also claims the benefit of priority to U.S. ProvisionalPatent Application No. 60/916,748, titled “CHARGING AND POWERING MOBILEDEVICES, BATTERIES”, filed May 8, 2007; U.S. Provisional PatentApplication No. 60/952,835, titled “INDUCTIVE CHARGING OF PORTABLEDEVICES”, filed Jul. 30, 2007; U.S. Provisional Patent Application No.61/012,922, titled “WIRELESS CHARGER WITH POSITION INSENSITIVITY”, filedDec. 12, 2007; U.S. Provisional Patent Application No. 61/012,924,titled “CONTROL, REGULATION, AND COMMUNICATION IN CHARGERS”, filed Dec.12, 2007; U.S. Provisional Patent Application No. 61/015,606, titled“PORTABLE INDUCTIVE POWER SOURCE”, filed Dec. 20, 2007; and U.S.Provisional Patent Application No. 61/043,027, titled “INDUCTIVE POWERSOURCE AND CHARGING SYSTEM”, filed Apr. 7, 2008; which application isalso related to U.S. patent application Ser. No. 11/757,067, titled“POWER SOURCE, CHARGING SYSTEM, AND INDUCTIVE RECEIVER FOR MOBILEDEVICES”, filed Jun. 1, 2007, which is now U.S. Pat. No. 7,948,208,issued May 24, 2011; each of which above applications are hereinincorporated by reference.

COPYRIGHT NOTICE

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

FIELD OF INVENTION

The invention is related generally to power supplies, power sources, andparticularly to a system and method for inductive charging of portabledevices.

BACKGROUND

There is currently a need for powering portable or mobile devices foruse in commercial, business, personal, consumer, and other applications.Examples of such devices include cellular telephones, personal digitalassistants (PDAs), notebook computers, mobile email devices, Blackberrydevices, Bluetooth headsets, hearing aids, music players (for example,MP3 players), radios, compact disk players, video game consoles, digitalcameras, walkie-talkie or other communication devices, GPS devices,laptop computers, electric shavers, and electric toothbrushes. Most ofthese devices include a rechargeable internal battery that must be firstcharged by an external power supply or charger, before the device itselfcan be used. The power supply typically provides direct current (DC)voltage through a special connector to the device. The power supply canthen be disconnected, and the device will continue to run for a shortperiod of time until the battery is depleted. The voltage and powerrequirements of the different devices vary, and to date there iscurrently no standardized connector for the devices. As a result ofthis, each mobile device is invariably sold or distributed bundled withits own charger. The costs associated with these multiple differenttypes and numbers of charger are paid by the consumer indirectly bybeing incorporated into the prices being charged for the mobile device.

The rapid increase in the total number and variety of mobile productshas meant that most people have several of the above-mentioned devices.In a typical day, that user would have to separately connect theirmultiple devices to each of their appropriate chargers for charging ofeach device. In addition, many people find it necessary to charge theirdevices in different locations such as their offices and cars. Thus,many users have purchased additional chargers for their offices andcars, for use in charging their mobile phones, notebook computers, andmusic players in those locations.

It will be evident that the above situation has caused typical users tohave a multitude of incompatible devices (i.e. power supplies andchargers) that essentially provide the same function of charging amobile device, but because of the number and variety that must be keptby the user are inconvenient to use. In many situations, users simplyforget to charge their devices, or else find they need to recharge theirdevice in situations where no appropriate charger is available. Thisleads to loss of ability to use the device when desired or needed.

In addition, when traveling way from home, mobile users have aparticular problem in that they need to pack and carry the multiplechargers for their devices. In many situations, these chargers arebulkier and heavier than the devices themselves, and use of thesedevices in foreign countries requires clumsy adaptors, and sometimesvoltage converters. This leads to a high degree of inconvenience for theever-more-mobile consumer.

In addition, the power connector for the mobile devices is often cheaplymanufactured, and a source of mechanical and electrical failure. In manyapplications, such as toothbrushes or applications where the device isexposed to water and needs to be hermetically sealed, such a physicalconnection can not be used. Thus an alternative means of powering thosetypes of devices must be used.

Several products have tried to address this situation. Some companiespropose the use of a universal charger that consists of a power supplybase unit, and interchangeable tips that both fit into the base unit andin turn fit different devices. The tip includes a customized regulatorthat sets the voltage required by the particular device. However, a usermust carry the multiple tips he or she needs for each of the variousdevices they have, and then charge each device serially by connectingthe device to the power supply. While this product reduces the overallweight of the charging tools the user must carry, the user still needsto carry and exchange the tips to connect to different devices. Inaddition, the charging of multiple devices simultaneously is often notpossible.

Realizing that a power supply typically contains a transformer forvoltage conversion, another approach is to split the transformer intotwo parts: a first part can contain the first winding and theelectronics to drive this winding at the appropriate operatingfrequency, while the second part consists of a winding where power isreceived and then rectified to obtain DC voltage. If the two parts arebrought into physical proximity to each other, power is transformed fromthe first part to the second inductively, i.e. by induction, without anyphysical electrical connection. This is the approach that is used inmany electrical toothbrushes, shavers, and other products that areexpected to be used in wet environments. However, a common problem withsuch inductive units is that the windings are bulky, which restrictstheir use in lightweight portable devices. Furthermore, to achieveadequate power transfer, the parts must be designed to fit togethersuitably so that their windings are closely aligned. This is typicallydone by molding the device casing (for example, an electric toothbrush)and its charger/holder so that they fit together in only one suitableway. However, the molded base and shape of the portable device meansthey cannot be used in a universal fashion to power other devices.

Some companies have proposed pad-like charging devices based oninductive concepts, but that also ostensibly allow for different typesof devices to be charged. These pads typically include grids of wires inan x and y direction, that carry an electrical current, and thatgenerate a uniform magnetic field parallel to the surface of the pad. Areceiver coil wound around a magnetic core lies on the surface of thepad and picks up the magnetic field parallel to the surface, and in thismanner energy can be transferred. However, each of these methods sufferfrom poor power transfer, in that most of the power in the primary isnot picked up in the receiver, and thus the overall power efficiency ofthe charger is very low. In addition, the magnetic cores used for theprimary and receiver are often bulky and add to the total cost and sizeof the system, and limit incorporation into many devices.

Another point to note is that, while all of the above devices allow auser to charge a device, they also require the charging device or baseunit to be electrically connected to a power source, such as a poweroutlet or a DC source. In many cases, the user may not have access tosuch a power source such as when traveling, camping, or working in anarea without access to power. However, to date, no device has beenprovided that is portable, and that allows for inductive charging ofmultiple devices with differing power requirements, and which itself canbe intermittently or occasionally charged either by an external powersource, or by other means, or that is self-powered or includes its ownpower source.

SUMMARY

A portable inductive power source, power device, or unit, for use inpowering or charging electrical, electronic, battery-operated, mobile,and other devices or rechargeable batteries is disclosed herein. Inaccordance with an embodiment the system comprises 2 parts: The firstpart is a pad or similar base unit that contains a primary, whichcreates an alternating magnetic field by means of applying analternating current to a winding, coil, or any type of current carryingwire. The second part of the system is a receiver that comprises a meansfor receiving the energy from the alternating magnetic field from thepad and transferring it to a mobile or other device or rechargeablebattery. The receiver may comprise coils, windings, or any wire that cansense a changing magnetic field, and rectify it to produce a directcurrent (DC) voltage, which is then used to charge or power the device.

In some embodiments the receiver can also comprise electronic componentsor logic to set the voltage and current to the appropriate levelsrequired by the mobile device or the charging circuit in the device, orto communicate information to the pad. In additional embodiments, thecharging or power system can provide for additional functionality suchas communication of data stored in the electronic device or to betransferred to the device. Some embodiments may also incorporateefficiency measures that improve the efficiency of power transferbetween the charger and receiver, and ultimately to the mobile device orbattery. In accordance with an embodiment the charger or power supplyincludes an internal battery for self-powered operation. In accordancewith other embodiments the charger or power supply can include a solarcell power source, hand crank, or other means of power supply foroccasional self powered operation. Other embodiments can be incorporatedinto charging kiosks, automobiles, trains, airplanes, or other transportand other applications.

In accordance with various embodiments, additional features can beincorporated into the system to provide greater power transferefficiency, and to allow the system to be easily modified forapplications that have different power requirements. These includevariations in the material used to manufacture the primary and/or thereceiver coils; modified circuit designs to be used on the primaryand/or secondary side; and additional circuits and components thatperform specialized tasks, such as mobile device identification, andautomatic voltage or power-setting for different devices.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a pad using multiple transmitter or charger coils inaccordance with an embodiment.

FIG. 2 shows a figure of a circuit diagram in accordance with anembodiment.

FIG. 3 shows a charging pad using multiple coils in accordance with anembodiment.

FIG. 4 shows a charging pad using multiple overlapping coil layers inaccordance with an embodiment.

FIG. 5 shows the use of multiple coil types and sizes in overlapping padlayers in accordance with an embodiment.

FIG. 6 shows a receiver with an integrated battery in accordance with anembodiment.

FIG. 7 shows a coupling of receiver with a device to be charged orpowered in accordance with an embodiment.

FIG. 8 shows a pad allowing modular or multiple connectivity inaccordance with an embodiment.

FIG. 9 shows a figure of a circuit diagram in accordance with anembodiment.

FIG. 10 shows a figure of a circuit diagram in accordance with anembodiment.

FIG. 11 shows a figure of a circuit diagram in accordance with anembodiment.

FIG. 12 shows a figure of power transfer chart in accordance with anembodiment.

FIG. 13 shows a figure of a coil layout in accordance with anembodiment.

FIG. 14 shows a figure of a coil layout in accordance with anembodiment.

FIG. 15 shows a figure of a charging pad with multiple coils inaccordance with an embodiment.

FIG. 16 shows a figure of a charging pad with movable coils and twodevices receiving power or charge in accordance with an embodiment.

FIG. 17 shows a figure of a circuit diagram in accordance with anembodiment.

FIG. 18 shows an illustration of a means of stacking coils, inaccordance with an embodiment.

FIG. 19 shows a figure of a circuit diagram for identificationverification in accordance with an embodiment.

FIG. 20 shows a figure of a circuit diagram for bidirectionalcommunication in accordance with an embodiment.

FIG. 21 shows a figure of a circuit diagram for output controller inaccordance with an embodiment.

FIG. 22 shows a figure of a circuit diagram for the receiver withregulator in accordance with an embodiment.

FIG. 23 shows a figure of a circuit diagram for MCU regulation inaccordance with an embodiment.

FIG. 24 shows a figure of a circuit diagram for unidirectionalcommunication in accordance with an embodiment.

FIG. 25 shows a figure of a circuit diagram for time-based regulation inaccordance with an embodiment.

FIG. 26 shows a high level view of a flyback power supply geometry inaccordance with an embodiment.

FIG. 27 shows an embodiment in which the output voltage to a load ismonitored and with changes in the load condition, a chip or a MicroController Unit (MCU) varies the frequency or the duty cycle of the FETdriver to achieve optimum operation.

FIG. 28 shows an implementation of a charger in accordance with anembodiment, wherein the primary stage and the receiver stage communicatewirelessly.

FIG. 29 shows an embodiment that includes Zero Voltage Switching (ZVS).

FIG. 30 shows an embodiment in which, instead of a digital feedbackcircuit, an analog circuit based on coupling between a light emittingdiode (LED) and a light detector can be used.

FIG. 31 shows an embodiment in which the opto-coupler is replaced by aVoltage Controlled Oscillator (VCO) and FET and in the primary, thesignal is sent to adjust a frequency controller to provide optimumoutput voltage.

FIG. 32 shows an embodiment in which the wireless link can be analog ordigital or can be integrated into the device to take advantage ofexisting wireless links in the device.

FIG. 33 shows a basic schematic for an inductive single coil chargingsystem in accordance with an embodiment.

FIG. 34 shows the main components of a wireless power/charging system inaccordance with an embodiment.

FIG. 35 shows a typical experimental curve for power transferred andPower Transfer in accordance with an embodiment.

FIG. 36 shows an embodiment in which a coil mosaic is used to cover thesurface area of a pad.

FIG. 37 shows an embodiment in which the number of drive (and sensing)circuits may be reduced by using electrical or electronic switches.

FIG. 38 shows an embodiment in which three coil layer printed circuitboard (PCB) is arranged to provide a cluster for uniform power in anarea using only one coil powered at any given time.

FIG. 39 shows an embodiment in which the coils are arranged such that bypowering only one of the coils in the cluster, any receiver coil placedwith a center within any location in the effective area can receive thespecified power if the appropriate charger coil is activated.

FIG. 40 shows an embodiment in which the number of switches required isreduced.

FIG. 41 shows an embodiment of a multi-charger pad that incorporates aplurality of charging clusters.

FIG. 42 shows an embodiment that uses a cluster of two layers of threecoils and a central coil to create an effective area.

FIG. 43 shows a mosaic of hexagonal coils with the central port to eachcoil shown as circles.

FIG. 44 shows an embodiment of a MEMS pad including the top view.

FIG. 45 shows an embodiment of a MEMS pad including a segmented MEMScharger pad.

FIG. 46 shows an embodiment in which one or more regulated powersupplies are connected to the charger pad.

FIG. 47 shows an array of contacts on the surface of a pad in accordancewith an embodiment.

FIG. 48 shows the side view of a MEMS conductive charger pad inaccordance with an embodiment.

FIG. 49 shows an embodiment wherein several regulated power suppliesprovide power to the pad, to allows charging of several devicessimultaneously.

FIG. 50 shows an alternative embodiment of a pad using a segmentedsurface.

FIG. 51 shows an industry standard means that is used for measuringemissions from a product.

FIG. 52 shows an embodiment which illustrates absorption through acopper layer.

FIG. 53 shows attenuation values for Copper and Aluminum layers forseveral thicknesses.

FIG. 54 shows transmitted power through Copper and Aluminum layers ofvarying thickness for an incident field at 1 MHz.

FIG. 55 shows an embodiment which allows for obtaining local alignmentindependence between coils in the charger and the receiver.

FIG. 56 show an embodiment in which coil magnets can divided intosections.

FIG. 57 shows an embodiment in which one or more alignment magnets canbe used behind each coil.

FIG. 58 shows an illustration of a device for inductive power chargingthat includes an internal battery for self-powered operation, inaccordance with an embodiment.

FIG. 59 shows an illustration of an inductive charger unit with a solarcell power source for self powered operation, in accordance with anembodiment.

FIG. 60 shows an illustration of an inductive charger unit with anincorporated communications and/or storage unit, in accordance with anembodiment.

FIG. 61 shows an illustration of a kiosk that incorporates an inductivecharger unit in accordance with an embodiment.

FIG. 62 illustrates some common regular (non-charger) mobile phoneholders types, in accordance with an embodiment.

FIG. 63 illustrates various products for a music player that includes anexternal rechargeable battery pack, in accordance with an embodiment.

FIG. 64 illustrates a multi-function device that includes a hard drive,rechargeable battery, and wireless connectivity, in accordance with anembodiment.

FIG. 65 illustrates a system for use with a charger case to inductivelypower or charge a mobile device, in accordance with an embodiment.

FIG. 66 shows a pad using multiple receiver/energizer coils inaccordance with an embodiment.

FIG. 67 shows, in a multi-charger or power supply where multiple coilsare used, such a high heat conductivity layer may be repeated aroundeach coil or cover all areas between the multiple coils, in accordancewith an embodiment.

FIG. 68 shows a similar method that may be used for heat removal fromwound coils of other shape and type.

FIG. 69 shows an embodiment in which the layer can be patterned toprovide heat conductivity channels rather than a continuous layer.

FIG. 70 shows an illustration of the electronics for the PCB coilinductive charger and/or power supply or the inductive receiver asfabricated on the same PCB as the coil, in accordance with anembodiment.

FIG. 71 shows an embodiment in which magnets placed at the center of astationary coil or a moving, floating charger and/or power supply coiland the receiver coil can provide a method for alignment of the coilsand to achieve this result.

FIG. 72 shows an embodiment in which two or more magnets that do notcross the center of the coil are used.

FIG. 73 is an illustration that shows how the magnets may be placedoutside the PCB coil area, in accordance with an embodiment.

FIG. 74 shows an embodiment in which magnetic arc-shaped parts around acircular coil are used.

FIG. 75 illustrates the use of bar magnets on or around the coil, inaccordance with an embodiment.

DETAILED DESCRIPTION

A portable inductive power source, power device, or unit, for use inpowering or charging electrical, electronic, battery-operated, mobile,rechargeable batteries, and other devices is disclosed herein. Inaccordance with an embodiment the system comprises two parts: The firstpart is a pad or similar base unit that contains a primary, whichcreates an alternating magnetic field by means of applying analternating current to a winding, coil, or any type of current carryingwire. In some embodiments the pad can also contain various signaling,and switching or communication circuitry, or means of identifying thepresence of devices or batteries to be charged or powered. In someembodiments the pad can also contain multiple coils or sections tocharge or power various devices or to allow charging or powering ofdevices or batteries placed anywhere on the pad. The second part of thesystem is a receiver that comprises a means for receiving the energyfrom the alternating magnetic field from the pad and transferring it toa mobile battery, or other device. The receiver can comprise coils,windings, or any wire that can sense a changing magnetic field, andrectify it to produce a direct current (DC) voltage, which is then usedto charge or power the device or battery.

In some embodiments the receiver can also comprise electronic componentsor logic to set the voltage and current to the appropriate levelsrequired by the mobile device or battery. In some embodiments, thereceiver can also contain circuitry to sense and determine the status ofthe electronic device or battery to be charged, the battery inside adevice, or a variety of other parameters and to communicate thisinformation to the pad. In additional embodiments, the system canprovide for additional functionality such as communication of datastored in the electronic device (for example, digital images stored incameras, telephone numbers in cell phones, songs in MP3 players) or datainto the device.

Embodiments can also incorporate efficiency measures that improve theefficiency of power transfer between the charger or power supply and thereceiver, and ultimately to the mobile device or battery. In accordancewith an embodiment, the charger or power supply comprises a switch, (forexample, a MOSFET device or another switching mechanism), that isswitched at an appropriate frequency to generate an alternative current(AC) voltage across a primary coil, and generates an AC magnetic field.This field in turn generates a voltage in the coil in the receiver thatis rectified and then smoothed by a capacitor to provide power to aload, with the result being greater efficiency.

In accordance with other embodiments the coils are mounted such thatthey can move laterally within the pad and within an area of theirsegments, while continuing to be connected to their driver electronicsplaced on the edges of the area. The floating coils and the drivecircuit are sandwiched in between thin upper and lower cover layers thatact to allow the coils lateral movement while limiting verticalmovement. When a receiver is placed on the pad, the pad senses theposition of the receiver coil and moves the coils to the right positionto optimize power transfer. Magnets can be used to better orient thecoils and improve greater power transfer efficiency.

Additional embodiments are also described herein. For example, inaccordance with an embodiment the charging/power supply device includesan internal battery for self-powered operation. In accordance with otherembodiments the charging/power supply device can include a solar cellpower source, hand crank, or other means of power supply for occasionalself powered operation. Other embodiments can be incorporated intocharging kiosks, automobiles, computer cases, and other electronicdevices and applications.

Inductive Charging System

While the above mentioned technologies describe various aspects ofinductive charging, they do not address the basic requirements that aconsumer and manufacturer desire in such a product. These include thefollowing desired features:

-   -   The pad should be able to charge or power a number of devices or        batteries with various power requirements efficiently. A typical        number may be one to six or even 12 or more devices or        batteries, including four or more low power (up to 5 W) devices        or batteries simultaneously. When multiple devices or batteries        are being charged, a method for energizing only those coils near        a device or battery is preferable.    -   The same pad should be able to power low-power devices (mobile        phones, PDAs, cameras, game consoles, etc.) or batteries with        power requirements of 5 W or less, and higher-power devices such        as notebook computers (which often have a power requirement of        60 W or higher) or high power batteries.    -   The power transfer efficiency between the primary coil and the        receiver should be maximized. Lack of efficiency in the power        transfer would necessitate larger and heavier AC to DC power        supplies. This would add cost and decrease product        attractiveness to customers. Thus methods where the entire pad        is energized are not as attractive.    -   A simple method for verification of the manufacturer of the        receiver, and possibly information for power requirements,        should be supported as necessary to ensure product compatibility        and to provide means of product registration and licensing.    -   The EMI radiation from the system should be minimized, and        ideally, the system should radiate little or no EMI with no        device present. A charger should preferably not emit any power        until an appropriate device or battery is brought close to the        charger or power supply itself. In this way, electric power is        not wasted, and electromagnetic power is not emitted needlessly.        In addition, accidental effects on magnetically sensitive        devices such as credit cards, disk drives and such are        minimized.    -   The pad and the receiver should be reasonably simple to        construct, and cost effective. Since both parts can be        integrated into mobile devices or batteries, the overall size,        weight, and form factor should be minimized.

As used herein, the term “charger” can refer to a device for supplyingpower to a mobile or stationary device for the purpose of eithercharging its battery, operating the device at that moment in time, orboth. For example, as is common in portable computers, the power supplycan operate the portable computer, or charge its battery, or accomplishboth tasks simultaneously. The charger may include circuitry for drivinga coil appropriately to generate an AC magnetic field, power or currentsense or regulation circuitry, microcontrollers, and means ofcommunication with a receiver, battery, or device. It may also be ableto communicate data with a device or battery or perform other functions.As used herein, the term ‘receiver’ means an inductive coil or coils andthe circuitry for rectification and smoothing of received current, anypossible control or communication circuitry for communication with thecharger and regulation of power and any possible circuit for managingcharging or measurement of status of a battery or a device to be chargedor powered such as a charge management circuit, fuel gauge, current,voltage, or temperature sensor, etc. The receiver can also incorporateappropriate circuitry for data transfer between a device or battery andthe charger. In accordance with an embodiment, the mobile device chargerand/or power supply can have any suitable configuration, such as theconfiguration of a flat pad. The power received by the mobile devicefrom the mobile device charger/power supply (such as the primary in themobile device charger) can be rectified in the receiver and smoothed bya capacitor before being connected to the rechargeable battery which isrepresented by the load in the figures. To ensure proper charging of thebattery, a regulator or charge management circuit can be placed betweenthe output of the output of the rectifier/capacitor stage and thebattery. This regulator or charge management circuit can sense theappropriate parameters of the battery (voltage, current, capacity), andregulate the current drawn from the receiver appropriately. The batterycan contain a chip with information regarding its characteristics thatcan be read out by the regulator or charge management circuit.Alternatively, such information can be stored in the regulator or chargemanagement circuit for the mobile device to be charged, and anappropriate charging profile can also be programmed into the regulatoror charge management circuit.

FIG. 1 shows a pad using multiple receiver/energizer coils in accordancewith an embodiment. In its simplest format, the mobile device or batterycharger or power supply preferably has a substantially flatconfiguration, such as the configuration of a pad 100, and comprisesmultiple coils or sets of wires 104. These coils or wires can be thesame size as or larger than the coils or wires in the mobile devices, orbattery and can have similar or different shapes, including for examplea spiral shape. For example, for a mobile device charger or power supplydesigned to charge or provide power to up to four mobile devices ofsimilar power (up to 10 W each) such as mobile phones, MP3 players,batteries, etc., four or more of the coils or wires will ideally bepresent in the mobile device or battery charger. The charger or powersupply pad can be powered by plugging into a power source such as a wallsocket or itself be powered or charged inductively. The pad can also bepowered by another electronic device, such as the pad being poweredthrough the USB outlet of a laptop or by the connector that laptops haveat the bottom for interfacing with docking stations, or powering otherdevices. The pad can also be incorporated into a docking station, suchas may be used by notebook computers or built into a table or othersurface.

In accordance with an embodiment, a mobile device can include a receiverthat includes one or more coils or wires to receive the power from themobile device charger or power supply. As described in further detailbelow, the receiver can be made part of the battery in the mobile deviceor of the shell of the mobile device. When it is part of the mobiledevice shell, the receiver can be part of the inside surface of themobile device shell or of the outside surface of the mobile deviceshell. The receiver can be connected to the power input jack of themobile device or can bypass the input jack and be directly connected tothe battery or charge management circuit inside the mobile device. Inany of these configurations, the receiver includes one or moreappropriate coil or wire geometries that can receive power from themobile device charger or power supply when it is placed adjacent to themobile device charger or power supply. In accordance with an embodiment,the coils in the mobile device charger or power supply and/or the coilsin the mobile devices or battery can be printed circuit board (PCB)coils, and the PCB coils can be placed in one or more layers of PCB.

In some embodiments, the charger or power supply can also itself bebuilt into a mobile device or battery. For example, a laptop computer orother portable or mobile device can incorporate a charger or powersupply section so that other mobile devices can be charged or powered asdescribed above. Alternatively, using the same set of coils or wires, ora separate set of coils or wires, any mobile device or battery canitself be used as an inductive charger or power supply to power orcharge other mobile devices or batteries.

In accordance with an embodiment, the mobile device charger/power supplyor pad, and the various mobile devices or batteries, can communicatewith each other to transfer data. In one embodiment, the coils in themobile device charger/power supply that are used for powering orcharging the mobile device, or another set of coils in the same PCBlayer or in a separate layer, can be used for data transfer between themobile device charger/power supply and the mobile device to be chargedor powered or the battery directly. Techniques employed in radio andnetwork communication, such as radio frequency identification (RFID),Bluetooth, WiFi, Wireless USB, or others can be used. In one embodimenta chip connected to an antenna (for example, the receiver coil orseparate data antenna) or another means of transfer of information canbe used to provide information about, for example, the presence of themobile device or battery, its authenticity (for example its manufacturercode) and the devices' charging/power requirements (such as its requiredvoltage, battery capacity, and charge algorithm profile).

In accordance with an embodiment, a typical sequence for charger/powersupply operation is as follows:

-   -   The mobile device charger or power supply can be in a low power        status normally, thus minimizing power usage.    -   Periodically, each of the coils (or a separate data coil in        another PCB layer) is powered up in rotation with a short signal        such as a short radiofrequency (RF) signal that can activate a        signal receiver in the receiver such as an RF ID tag or a        circuitry connected to the receiver coil.    -   The mobile device charger/power supply then tries to identify a        return signal from any mobile device, battery (or any receiver)        that may be nearby.    -   Once a mobile device, or battery (or a receiver) is detected,        the mobile device charger or power supply and the mobile device        or battery to proceed to exchange information.    -   This information can include a unique ID code that can verify        the authenticity and manufacturer of the charger or power supply        and mobile device or battery, the voltage requirements of the        battery or the mobile device, and the capacity of the battery.        For security purposes or to avoid counterfeit device or pad        manufacture, such information can be encrypted, as is common in        some RFID tags or other verification systems.

In accordance with various embodiments, other protocols such as NearField Communications (NFC) or Felica can be used, wherein the circuitrycontaining the ID and the necessary information is powered either by themobile device or battery or remotely by the mobile device charger orpower supply. Depending on the particular implementation needs,Bluetooth, WiFi, Wireless USB, and other information transfer processescan be used. Additional information regarding the charging profile forthe battery can also be exchanged and can include parameters that areused in a pre-programmed charge profile stored in the mobile device orbattery charger. However, the information exchanged can be as simple asan acknowledge signal that shows the mobile device charger that a mobiledevice or rechargeable battery is present. The charger or power supplycan also contain means for detection and comparison of the strength ofthe signal over different locations on the charger or power supply. Inthis way, it can determine the location of the mobile device or batteryon the charger or power supply, and then proceed to activate theappropriate region for charging or powering.

In some embodiments that require greater simplicity, no communicationneed take place between the mobile device charger or power supply andthe mobile device or battery. In some embodiments the mobile devicecharger or power supply can sense the mobile device or battery bydetecting a change in the conditions of a resonant circuit in the mobiledevice charger or power supply when the mobile device or battery isbrought nearby. In other embodiments the mobile device or battery can besensed by means of a number of proximity sensors such as capacitance,weight, magnetic, optical, or other sensors that determine the presenceof a mobile device or battery near a coil in the mobile device orbattery charger or power supply. Once a mobile device or battery issensed near a primary coil or section of the mobile device or batterycharger or power supply, the mobile device charger or power supply canthen activate that primary coil or section to provide power to thereceiver coil in the mobile device's battery, shell, receiver module,battery, or the device itself.

Inductive Charging Circuit

Each mobile device and its battery has particular characteristics(voltage, capacity, etc.). In order to facilitate these differentdevices or batteries with a single universal mobile device charger orpower supply, several circuit architectures are possible, some of whichare described in further detail below.

FIG. 2 shows the main components of a typical inductive power transfersystem 110. The circuit illustrated is used to illustrate the principleof inductive power transfer and is not meant to be limiting to anembodiment. In accordance with an embodiment, the charger 112 comprisesa power source 118, and a switch T 126 (which can be a MOSFET or otherswitching mechanism) that is switched at an appropriate frequency togenerate an AC voltage across the primary coil Lp 116 and generate an ACmagnetic field. This field in turn generates a voltage in the coil 120in the receiver 114 that is rectified and then smoothed by a capacitorto provide power 122 to a load RI 124. For ease of use, a receiver canbe integrated with a mobile device, such as integrated inside the mobiledevice or attached to the surface of the mobile device duringmanufacture, to enable the device to receive power inductively from amobile device charger or integrated into, or on its battery.

In accordance with an embodiment, the circuit shown in FIG. 2 canreceive energy fed to it from a power source, store the energyalternately in the inductor and the timing capacitor (much like a tankstores liquid), and subsequently produce an output as a continuousalternating current (AC) wave. As the voltage is applied to the primaryside, the tank circuit supplies the energy to the receiver. One of thebenefits of such a design is that the timing capacitor in the circuitcan be easily replaced. For example, if a relatively higher value forcapacitance (referred to in some instances as a timing capacitance) isused, then the frequency of operation is lowered. This increases theon-time for the circuit, and provides longer power transfer and currentthrough the transformer, and thus more power. As such a higher value ofcapacitance can be used for high power applications. Conversely, if arelatively lower value for capacitance is used, then the frequency ofoperation is increased. This reduces the on-time and provides less powertransfer and current through the transformer, and thus less power. Thus,a lower value of capacitance can be used for low power applications.Replacing the timing capacitance can be easily handled duringmanufacturing to tune the power requirement on a macro level, i.e. toget the output into an appropriate range for the chosen application.Additional techniques can then be used to set the voltage output on amore accurate basis.

The mobile device or its battery typically can include additionalrectifier(s) and capacitor(s) to change the AC induced voltage to a DCvoltage. This is then fed to a regulator/charge management chip whichincludes the appropriate information for the battery and/or the mobiledevice. The mobile device charger provides power and the regulation isprovided by the mobile device. The mobile device or battery charger orpower supply, after exchanging information with the mobile device orbattery, determines the appropriate charging/powering conditions to themobile device. It then proceeds to power the mobile device with theappropriate parameters required. For example, to set the mobile devicevoltage to the right value required, the value of the voltage to themobile device charger can be set. Alternatively, the duty cycle of thecharger switching circuit or its frequency can be changed to modify thevoltage in the mobile device or battery. Alternatively, a combination ofthe above two approaches can be followed, wherein regulation ispartially provided by the charger or power supply, and partially by thecircuitry in the receiver.

Inductive Charger Pad

To allow the operation of the mobile device or battery charger or powersupply regardless of position of the mobile device or battery, the totalarea of the mobile device or battery charger or power supply can becovered by coils or by another wire geometry that creates magneticfield.

FIG. 3 shows a charging pad using multiple coils in accordance with anembodiment. As shown in FIG. 3, in accordance with an embodiment the pad140 is largely covered with individual receiver coils 144.

FIG. 4 shows a charging pad using multiple overlapping coil layers inaccordance with an embodiment. This embodiment addresses the problem ofvoids between the multiple coils. As shown in FIG. 4, any areas of thepad 150 with minimal magnetic field between a first set of coils 152 canbe filled by a second set of coils 154, so that the coils are tiled suchthat the centers of this coil array fill the voids in the primary set.This second set can be at a different layer of the same PCB, or in adifferent PCB. In each of these geometries, the sensing circuitry canprobe each location of a coil in a raster, predetermined, or randomfashion. Once a mobile device or battery on or near a coil is detected,that coil is activated to provide power to the receiving unit receiverof the appropriate device.

It can be seen from the above example that by providing more layers ofthe PCB with coils, or by providing coils of different geometry or size,one can obtain as much resolution or coverage as desired.

In accordance with an embodiment, to power mobile devices or batterieswith power requirements that exceed maximum powers attainable by typicalcoils in a surface, the mobile device or battery, during its hand shakeand verification process can indicate its power/voltage requirements tothe mobile device or battery charger or power supply. Several geometriesfor achieving power/voltage levels otherwise not attainable from asingle primary coil of the mobile device or battery charger or powersupply are possible.

In accordance with one embodiment of the system geometry, the powerreceiving unit of the mobile device or battery has several coils orreceiving units that are connected such that the power from severalprimary coils or sets of wires of the mobile device or battery chargeror power supply can add to produce a higher total power. For example, ifeach primary coil is capable of outputting a maximum of 10 Watts, byusing six primary coils and six receiver coils, a total output power of60 Watts can be achieved. The number of primary and receiver coils neednot be the same, and a large receiver coil (receiving unit) that is ableto capture the majority of magnetic flux produced by 6 or other numberof primary coils or a large primary coil powering six or another numberof receiver coils can achieve the same effect. The size and shape of themultiple primary coils and receiver coils also do not need to be thesame. Furthermore, neither set of primary and receiver coils need to bein the same plane or PCB layer. For example, the primary coils in theexamples shown above can be dispersed such that some lay on one PCBplane and the others in another plane.

In accordance with another geometry, the PCB of the mobile device orbattery charger or power supply has multiple layers, wherein coils orwire patterns of certain size and power range can be printed on one ormore layers and other layers can contain coils or wire patterns oflarger or smaller size and power capability. In this way, for example,for low power devices, a primary from one of the layers will providepower to the mobile device or battery. If a device or battery withhigher power requirements is placed on the pad, the mobile device orbattery charger or power supply can detect its power requirements andactivate a larger coil or wire pattern with higher power capabilities ora coil or wire pattern that is connected to higher power circuitry. Onemay also achieve similar results by using a combination of the differentprocesses and geometries described above.

FIG. 5 shows the use of multiple coil types and sizes in overlapping padlayers in accordance with an embodiment. As shown in FIG. 5, the mobiledevice or battery charger or power supply or pad 160 can comprise twooverlapping layers with a first layer 162 containing low power coils,and a second layer 164 containing high power coils.

Inductive Charging Receiver

As described above, the inductive charging or power supply pad is usedto power a receiver, which in turn is used to power or to charge aportable or mobile device or battery. In accordance with one embodimentof the receiver, the power from the mobile device or battery charger orpower supply is emitted at a magnitude that is sufficient to power anyforeseeable mobile device or battery (such as 5 W or 10 W for smallmobile devices or batteries). The receiver that is appropriate for eachmobile device or battery has a power receiving part that when matched tothe mobile device or battery charger or power supply is able to receivesufficient power for the mobile device or battery. For example areceiver for a mobile phone requiring 2.5 W can be a coil with certaindiameter, number of turns, wire width, etc. to allow receipt of theappropriate power. The power is rectified, filtered, and then fed intothe battery or power jack of the device. As discussed above, a regulatoror charge management circuit can be used before the power is provided tothe battery or the mobile device.

To save energy, the power emitted by the mobile device or batterycharger or power supply can be regulated. It is desirable to regulatethe power emitted by the charger or power supply because if the chargeror power supply is emitting 10 W of power and the receiver is designedto receive 5 W, the rest of the emitted power is wasted. In oneembodiment, the receiver or the mobile device can, through an electrical(such as RF), mechanical, or optical method, inform the charger or powersupply about the voltage/current characteristics of the device orbattery. The primary of the charger or power supply in the circuitdiagrams shown above then can be driven to create the appropriatevoltage/current in the receiver. For example, the duty cycle of theswitch in that circuit can be programmed with a microprocessor to bechanged to provide the appropriate levels in the receiver.

In accordance with an embodiment, the programming can be performed by alook up table in a memory location connected to a microprocessor or byusing an algorithm pre-programmed into the microprocessor.Alternatively, the frequency of the switch can be changed to move thecircuit into, and out of, resonance to create the appropriate voltage inthe receiver. In an alternate geometry, the voltage into the circuitryin the primary can be changed to vary the voltage output from thereceiver. Furthermore, the induced voltage/current in the mobile devicecan be sensed and communicated to the charger to form a closed-loop, andthe duty cycle, frequency, and/or voltage of the switch can be adjustedto achieve the desired voltage/current in the mobile device.

In accordance with an embodiment, the receiver is built onto or into thebattery for the mobile device. The receiver can include one or morecoils or wires shaped to receive power from the charger or power supply.The one or more coils or wires can be either printed on one or morePCBs, or formed from regular wires. As described above, the receiver canalso contain rectifier(s) and capacitor(s) to produce a cleaner DCvoltage. This output can be directly, or through a current limitingresistor, connected to one of the contacts on the battery. To avoidovercharging the battery, a battery regulator or charge management chipcan also be used. This circuit then measures the various parameters ofthe battery (voltage, degree of charging, temperature, etc.) and uses aninternal program to regulate the power drawn from the circuit to ensureover-charging does not occur. The circuit can also include LEDs to showthe receiver being in the presence of a magnetic field from the charger,complete charge LEDs and/or audible signals.

In typical commercial and end-user applications, such as in cell phones,PDAs, and MP3 players, the battery can be incorporated into the batterypack or the device by the original equipment manufacturer (OEM), or asan after-market size and shape compatible battery pack that can replacethe original battery pack. The battery compartment in these applicationsis typically at the bottom of the device. The user can open the batterycompartment, take out the conventional battery, replace it with amodified battery in accordance with an embodiment, and then replace thebattery lid. The battery can then be charged inductively when the mobiledevice is placed adjacent a mobile device charger.

To enhance the ability of the receiver to receive power, it may bedesirable to minimize the distance between the charger's primary coiland the receiver's coil or wire. In order to achieve this, in accordancewith an embodiment the receiver's coil or wire can be put on the outsideof the battery pack.

FIG. 6 shows a battery with an integrated receiver in accordance with anembodiment. As shown in FIG. 6, the receiver 170 comprises the battery182, together with the receiver coil 172, and any rectifiers 174,capacitors 176, regulators or charge management chips 180 necessary forproper operation of the charging receiver. If the battery compartmentlid of the device prevents a power receiving light emitting diode (LED)to be seen, the lid can itself be replaced with a see-through lid or alid with a light pipe that will allow the user to see the chargingindicator LED when the mobile device is placed adjacent to the charger.

In an alternative embodiment, the receiver battery can include amechanical, magnetic, or optical method of alignment of the coils orwires of the charger and mobile device for optimum power transfer. Inaccordance with an embodiment, the center of the primary in the chargercontains a magnet such as a cylinder or disk or ring with the polesparallel to the charger surface and the magnetic field perpendicular tothe charger surface. The receiver also contains a magnet or magneticmetal part of a similar or different shape behind or in front of thecoil or wire receivers. When the mobile device or battery is placed onor adjacent to the charger or power supply, the magnets attract and pullthe two parts into alignment with the centers of the two coils or wiresaligned. The magnets do not need to be especially strong to actively dothis. Weaker magnets can provide guidance to the user's hand and largelyachieve the intended results. Alternatively, audible, or visual signs(for example an LED that gets brighter as the parts are closer aligned),or mechanical means (dimples, protrusions, etc.) can be used foralignment.

In accordance with another embodiment, the coil or wires and the magnetin the charger or power supply are mechanically attached to the body ofthe charger or power supply such that the coil can move to align itselfappropriately with the mobile device or battery when it is brought intoclose proximity to the charger or power supply. In this way, anautomatic alignment of coils or wire patterns can be achieved.

In another embodiment, the receiver electronics described above arepreferably made from flexible PCB which can be formed into a curvedshape. Such a PCB can be placed on the surface of a battery pack,including one that is not flat, or that has a curved shape. The curve onthe battery or back of a mobile device battery lid can be matched to acurved primary in the mobile device or battery charger or power supplyand be used for alignment. One example of usage of this embodiment canbe for example flashlights that have circular handles: the batteries canbe charged with coils on the side of circular batteries, or circling thecylindrical battery. Similarly, the mobile device or battery charger orpower supply can have a curved shape. For example, the charger or powersupply surface can be in the shape of a bowl or some similar object. Amobile device or battery that may have a flat or curved back can beplaced into the bowl. The shape of the bowl can be made to ensure thatthe coil of the mobile device or battery is aligned with a primary coilto receive power.

In another embodiment, the primary can be incorporated into a shape suchas a cup. A mobile device can be placed into the cup standing on end andthe receiver can be built-in to the end of the mobile device (such as amobile phone) or battery or on the back or circumference of the deviceor battery. The receiver can receive power from the bottom or wall ofthe cup.

In another embodiment, the primary of the charger can have a flat shapeand the mobile devices or battery can be stood up to receive power. Thereceiver is built into the end of the device or battery in this case anda stand or some mechanical means can be incorporated to hold the deviceor battery while being charged.

In another embodiment, the charger or power supply can be made to bemounted on a wall or a similar surface, vertically or at an angle (suchas on a surface in a car), so as to save space. The charger or powersupply can incorporate physical features, magnets, fasteners or the liketo enable attachment or holding of mobile devices to be charged. Thedevices or batteries to be charged or powered can also incorporate aretainer, magnet, or physical shape to enable them to stay on thecharger or power supply in a vertical, slanted, or some other position.In this way, the device or battery can be charged or powered by theprimary while it is near or on it.

For those applications where the lid of the battery compartment or thebottom part of the mobile device is made from a metal, a replacementnon-metallic lid or backing can be used. Alternatively, the coil can beattached to the outside of the metal surface. This allowselectromagnetic (EM) fields to arrive at the power receiver coil orwires. The rest of the receiver (i.e. circuitry) can be placed behind ametal for the receiver to work. In some other applications where thebattery has metal parts, these parts may interfere with the EM field andthe operation of the coil in the receiver. In these cases, it may bedesirable to provide a distance between the metal in the battery and thecoils. This can be done with a thicker PCB or battery top surface.Alternatively, to provide additional immunity, ferrite material (such asthose provided by Ferrishield Inc.) can be used between the receiver andthe battery to shield the battery or device from the EM fields. Thesematerials can be made so as to be thin, and then used during theconstruction of the integrated battery/receiver.

In accordance with another embodiment, the receiver in the battery ormobile device also includes a means for providing information regardingbattery manufacturer, required voltage, capacity; current, chargestatus, serial number, temperature, etc. to the charger. In a simplifiedembodiment, only the manufacturer, required voltage, and/or serialnumber is transmitted. This information is used by the charger or powersupply to adjust the primary to provide the correct charge or powerconditions. The regulator or charge management chip in the receiver canthen regulate the current and the load to charge the battery correctlyand can end charge at the end. In another embodiment, the receiver cancontrol the charging process fully depending on the time dependentinformation on battery status provided to it. Alternatively, thecharging process can be controlled by the charger in a similar manner.As described above, the information exchange between the charger and thereceiver can be through an RF link or an optical transmitter/detector,RFID techniques, Near-Field Communication (NFC), Felica, Bluetooth,WiFi, or some other method of information transfer. Similarly, thereceiver can send signals that can be used by the charger to determinethe location of the receiver to determine which coil or section of thecharger or power supply to activate. The communication link can also usethe same coil or wires as antenna for data transfer or use a separateantenna. In some embodiments the received can use the actualcapabilities of the mobile device (for example, the built-in Bluetoothor NFC capabilities of mobile phones) to communicated with the chargingor power supply pad.

As described above, in accordance with some embodiments the receiver canbe integrated into the body of the device or battery itself at alocation that may be appropriate and can be exposed to EM radiation fromoutside. The output of the receiver can be routed to the electrodes ofthe battery internally inside the device and appropriate circuitryinside the device can sense and regulate the power. The device caninclude LEDs, messages, etc. or audible signs that indicate to the userthat charging is occurring or complete or indicate the strength of thereceived power (i.e. alignment with a primary in the charger) or thedegree of battery charge. In other embodiments, the receiver is builtinto an inner or outer surface of a component that is a part of themobile device or battery's outer surface where it is closest to thecharger. This can be done as original equipment or as an after-marketitem. The component can be the lid of the battery pack or the bottomcover of the mobile device. In yet other embodiments, the receiver canbe integrated into the back or front of the battery compartment or aninterchangeable shell for the mobile device for use in after-marketapplications. For example, in a mobile phone application, the backbattery cover or shell can be removed and replaced with the new shell orbattery cover with the receiver built in.

FIG. 7 shows a coupling of receiver with a device to be charged orpowered in accordance with an embodiment. As shown in FIG. 7, theoriginal mobile phone setup 190 includes a device 192 with shell 194 andpower jack 196. The after-market modification 200 replaces the originalshell with a combination shell 210 that includes the necessary receivercoils and battery couplings. The contacts from this circuitry can thenmake direct contact to the battery electrodes inside the mobile deviceor to some contact points inside the mobile device if such contactsexist or become provisioned by the device manufacturer duringmanufacture. Alternatively, the receiver may be a component (such as ashell) that has a connector that plugs into the input power jack of themobile phone or electrodes of a battery. The receiver can be fixed to,or detachable from, the mobile device or battery. This can be achievedby having a plug that is attached either rigidly or by a wire to thereceiver (shell). Alternatively, the replacement receiver (shell) can belarger than the original shell and extend back further than the originalshell and contain the plug so that when the receiver (shell) isattached, simultaneously, contact to the input power jack is made.Alternatively, the receiver (shell) can have a pass-through plug so thatwhile contact is made to this input power connector, the connectorallows for an external regular power supply plug to be also used as analternative. Alternatively, instead of a pass-through, this part caninclude a power jack in another location in the back so that a regularpower supply can be used to charge the battery. In cases where theconnector to the device performs other functions such as communicationto the device, a pass-through connector can allowcommunication/connectivity to the device.

In accordance with another embodiment, the replacement receiver (i.e.the replacement shell) or the plug in unit, in addition to the powerreceiver components and circuitry, can include additional circuitry thatcan provide further functionalities to the mobile device. These caninclude, for example, the ability to exchange data through Bluetooth,WiFi, NFC, Felica, WiMax, RFID, or another wireless or opticalmechanism. It can also provide extended functionalities such as GlobalPositioning System (GPS) location information, flashing lights,flashlight, or other decorative or electronic functions. As describedabove, various methods for improving coil alignment, or location,battery manufacturer, or battery condition information transfer can alsobe integrated into the receiver or replacement shell.

In another embodiment, the receiver is supplied in the form of aseparate unit that is attached to the input jack of the mobile device orbattery or integrated into a receiver protective skin for the mobiledevice. Many leather or plastic covers for mobile phones, cameras, andMP3 players already exist. The primary purpose of these covers is toprotect the device from mechanical scratches, shocks, and impact duringdaily use. However, they typically have a mere decorative or advertisingapplication. In accordance with one embodiment, the receiver is formedof a thin PCB with the electronics formed thereon, and the receiver coilor wire that is attached to the back of the device and plugs into theinput jack similar to the shell described above. Alternatively, it canbe connected through a flexible wire or flexible circuit board that isrouted to a plug for the input power jack.

In accordance with another embodiment, the receiver can be a separatepart that gets plugged into the input jack during charging and is placedon the charger and can then be unplugged after charging is finished.

In another embodiment, the receiver is built in the inside or outsidesurface or in between two layers of a plastic, leather, silicone, orcloth cover for the mobile device and plugs in or makes contact to thecontact points on the device.

It will be noted that certain devices such as notebooks and some musicplayers have metal bottom surfaces. The methods described above forchanging the back surface or use of a plug in the mobile device or asecondary skin with an integrated receiver is particularly useful forthese applications. As described previously, the effect of the metalsurface can also be minimized, if necessary, by increasing the distancebetween the wires of the receiver and the metal surface or by placing aferrite layer in between the receiver and the metal bottom.

It is also noted that the use of methods such as curving the receiver orintegrating magnets, LEDs, audio signals or messages, etc. foralignment, or methods for location, manufacturer or charging conditionidentification, as described above are possible with all embodiments ofan embodiment described above. In any of the above cases, the charger orpower supply can contain lights, LEDs, displays, or audio signals ormessages to help guide the user to place the mobile device or battery ona primary coil for maximum reception, to show charging is occurring, andto show the device is fully charged. Displays to show how full thebattery is or other information can also be incorporated.

Flexible/Modular Charging Pad

In accordance with an embodiment a flexible mobile device charger orpower supply is provided in the shape of a pad that can be folded orrolled up for carrying. In one implementation of an embodiment, theelectronics of the charger or power supply are placed on a thin flexiblePCB or the coils are made of wires that can be rolled up or shaped. Theelectronics components made of silicon chips, capacitors, resistors andthe like may not be flexible but take up very little space. These rigidcomponents can be mounted on a flexible or rigid circuit board, whilethe main section of the pad containing the coils or wires for energytransfer can be made to be flexible to allow conformity to a surface orto be rolled up. Thus the pad resembles a thin mouse pad or the like.

In some cases, it may be advantageous to the user to have a mobiledevice charger or power supply that is extendible in functionalities.The cases include but are not limited to:

-   -   A user may purchase a mobile device or battery charger or power        supply for charging or powering a single low power device or        battery but, at a later stage, may want to extend the capability        to charge or power more devices or batteries simultaneously.    -   A user may purchase a mobile device or battery charger or power        supply for charging or supplying power to one or more low power        devices or batteries but may want to charge or supply power to        more low power or high power devices or batteries.    -   A user may buy a mobile device or battery charger or power        supply that can charge or supply power to one or more low-power        or high-power devices or batteries and later wish to have the        communication or local storage, or a rechargeable battery, or        means of power generation such as solar panels or some other        capability, added to the charger or power supply.

In all of the cases above and others, it can be useful to have a modularapproach to expand the capabilities of the mobile device or batterycharger or power supply.

FIG. 8 shows a pad 220 in accordance with an embodiment that allows formodular or multiple connectivity. In this case, the user can purchase afirst unit 222 that is powered by an electric outlet 224. However,interconnects 226 for power and data are provided so that additionalunits 228, 230 can simply fit or plug into this first one directly orindirectly and expand the capabilities as the customer's needs grow.Data communications and storage units 234 can also be attached in amodular fashion. This approach would enable the customer to use thetechnology at a low cost entry point and grow his/her capabilities overtime.

Some of the electronics devices that can benefit from these methodsinclude: mobile phones, cordless phones, personal data assistants(PDAs), pagers, walkie-talkies, other mobile communication devices,mobile electronic mail devices, Blackberry's, MP3 players, CD players,DVD players, game consoles, headsets, Bluetooth headsets, hearing aids,head-mounted displays, GPS units, flashlights, watches, cassetteplayers, laptops, electronic address books, handheld scanning devices,toys, electronic books, still cameras, video cameras, film cameras,portable printers, portable projection systems, IR viewers, underwatercameras or any waterproof device, toothbrushes, shavers, medicalequipment, scientific equipment, dental equipment, military equipment,coffee mugs, kitchen appliances, cooking pots and pans, lamps or anybattery, DC, or AC operated device.

In addition, inductive power transfer can provide power to devices thatare not so far battery operated. For example, a mobile device charger orpower supply in the shape of a pad placed on a desk or a kitchen tablecan be used to power lamps or kitchen appliances. In one embodiment forthe use in a kitchen, a flat charger, or power supply such as a pad,placed on or built into a counter can allow the chef to place devices onthe charger or power supply to be inductively charged or powered duringuse and simply place them away after use. The devices can be, forexample, a blender, mixer, can opener, or even pot, pan, or heater. Thiscan eliminate the need for a separate cooking and work area. It will benoted that placement of a metal pan close to the inductive pad candirectly heat the pan and the contents while keeping the charger orpower supply surface cool. Due to this reason, inductive kitchen rangeshave been commercialized and shown to be more efficient than theelectric ranges that work by resistive heating of a coil.

In another embodiment, rather than direct heating of metal pans bynearby inductive fields, cooking pans may include a receiver and heatingor even cooling elements. Once placed on a charger, the pan will heat upor cool down as desired by a dial or the like on the pan allowingprecise temperature control of the pan and the contents.

Similarly, in an office or work area setting, if a charger or powersupply is readily available for charging or powering mobile devices orbatteries, it can also be used to power up lamps for illumination of thedesk or used to power or charge office appliances, such as fax machines,staplers, copiers, scanners, telephones, and computers. In oneembodiment, the receiver can be built into the bottom of a table lampand the received power is used to power the incandescent or LED lamp.

In another embodiment, a mug, cup, glass, or other eating appliance suchas a plate can be fitted with a receiver at its bottom. The receivedpower can be used to heat the mug, etc. with a heating coil thus keepingbeverages or food warm to any degree desired. Furthermore, in accordancewith an embodiment, by use of devices such as thermoelectric coolers thecontents can be cooled or heated as desired.

Similarly, many children's toys often run out of battery power due toextended use or simple forgetfulness to turn the device off. Often thesebatteries are included inside a battery compartment that for safetyreasons can only be opened by a screwdriver. Inclusion of the receiverinto toys or batteries inside can reduce the need to change the devicebatteries and allow recharging with a much simpler method.

In another implementation, the receiver can be built into medicaldevices or their batteries that are implanted or inserted in the body.Since batteries in these devices such as pace makers, cochlear implants,hearing aids, or other monitoring devices may need periodic charging,inductive power transfer can provide an ideal non-contact method forcharging and testing the performance of the devices (i.e. check up) ordownloading data that the devices have logged.

In another implementation, some active RFID tags include batteries thatcan send out information about the status or location of a package orshipment. An inexpensive method for charging these tags is to include areceiver with each tag. Thus, a charger can be used to power or chargethese RFID tags.

It will be noted that the effective working distance of the inductivecharger is dependent on the power and the frequency of the source andthe size and geometry of the coil. By increasing the frequency toseveral or tens of MHz, one can obtain a working distance of severalinches or feet depending on the application for the technology. It willalso be noted that any of the above embodiments that eliminate the inputpower jack are especially important because they add to productreliability by removing a source of mechanical or environmental failure.In addition, elimination of the jack is imperative for water proofapplications and for extra safety.

Efficiency Enhancements through Coil Circuit

In accordance with an embodiment, in order for the power efficiency tobe maximized and to minimize losses in the coil, the coils should bemanufactured to have as low a resistance as possible. This can beachieved by use of more conductive material such as gold, silver, etc.However the costs of these materials are sometimes prohibitive. Inpractice, reduced resistivity can be obtained by using thickercopper-clad PCBs or wider tracks. Most common PCBs use 1-2 oz copperPCBs. In accordance with some embodiments the coil PCB used for thewireless charger can be made from PCBs clad with between 2 and 4, oreven 6 oz copper. The process of manufacture of the PCB can also beoptimized to achieve higher conductivity. For example, sputtered copperhas a higher conductivity than rolled copper and is typically better forthis application. In operation, the coil and the circuitry demonstrate aresonance at a frequency determined by the parameters of the design ofthe coil (for example, the number of windings, coil thickness, width,etc.). Previous work has concentrated on circuits driven by square waveswith a MOSFET. This approach has the disadvantage that since a squarewave is not a pure sinusoid, it produces harmonics. These harmonics areundesirable because:

-   -   The PCB coil produces optimum power transfer efficiency at a        particular frequency. The harmonics in the primary signal are        not transferred as efficiently and decrease the overall system        efficiency.    -   The rapid voltage change in the leading and falling edge of the        square wave creates oscillations that create further harmonics        resulting further EMI.    -   The harmonics radiated by the primary create higher frequency        components that contribute to the EMI that is more radiative        (due to higher frequency). It is desirable to limit the        frequency range of the operation of the overall system to as low        a frequency as possible while maintaining the other requirements        of the system (such as sufficient working distance, etc.), so        these harmonics must be avoided.    -   At the instance of switch turn-on and turn-off, the change in        the in-rush current to the coil causes huge voltage swings        across the coil for a short period of time. All the power is        transferred to the receiver during these times that are short.

Previous attempts to achieve 90% transfer efficiency with PCB coilprimary and receiver have used a laboratory power supply to drive theircircuit. While this approach has demonstrated the higher efficiency thatcan be achieved with a sinusoidal voltage on the coil, such powersupplies are complex, costly, and too large to be able to be used forany practical charger application. In accordance with an embodiment, acapacitor is added in parallel to the drain/source contacts of theMOSFET.

FIG. 9 shows a figure of a circuit diagram 240 in accordance with anembodiment. The coil in the wireless charger system is driven byswitching the FET at the resonance frequency of the circuit when thereceiver is present. Without the receiver nearby, the circuit is detunedfrom resonance and radiates minimal EMI. The capacitor 244 acts as areservoir of energy that discharges during switch off time and enhancesenergy transfer. As with the examples described above, changing thevalue of the capacitance allows for tuning the power and efficiencylevels on a lower-power/high-power basis, and additional features andtechniques can be used to fine tune the power output for particulardevices.

The circuit designs illustrated in FIG. 2 and FIG. 9 use a zero-crossingpower supply. Briefly, in a zero-crossing power supply, when thetransistor in the primary coil is first turned on, electrical currentpasses through the primary coil and the transistor to ground. When thetransistor is then turned off, the voltage level at the transistorswings high (for example, if the input voltage is 5V, then the voltagelevel may swing to 10V, or even 100V). A non-zero-crossing circuitallows the current to drop to zero, before the cycle is restarted. Aforward mode circuit can then use an inductor in series with the load torevive the current and charge up the inductor, while a diode allowscharging in both directions (when full phase AC is used).

In a traditional transformer design, zero-crossing is not used, since itinvariably results in lower efficiency compared to non-zero designs, atleast with higher power or ferrite cores. This is primarily because thetraditional ferrite cores act as capacitors and store energy, which inturn reduces the circuit efficiency. As described above, in accordancewith an embodiment, when a non ferrite coil there is no magnetic flux,so the efficiency is not affected to the same extent.

Furthermore, since the system does not use a ferrite or ferromagneticcore, the overall size and weight of the device can be reduced. Inaccordance with some embodiments the coil can be formed on a printedcircuit board (PCB), with no heavy ferrite coils, no soldering and nowiring to the coils. In accordance with some embodiments there is noneed for a magnetic core in the secondary in the receiver. Sincemagnetic cores are usually large and heavy this results in considerablesize savings.

By way of example, in accordance with an embodiment that uses anIRFR0220 chip as a FET and use 4 oz copper coils with 9 turns and 1.25″diameter, the circuit in FIG. 2 above, can be loaded with RL of 10 Ohmand tuned to operate at 1.3 MHz. With matching coils in the primary andsecondary in the receiver, without capacitor C, total circuit efficiencyof the circuit including the clock and FET driver circuit approaches48%. Addition of a 1600 pF capacitor in parallel to the FET increasesthe total circuit efficiency to 75% (a better than 50% increase inefficiency), while simultaneously decreasing the voltage across the FETand also the harmonics in the circuit. The coil to coil transferefficiency with the capacitor placed in parallel with the FET isestimated to be approximately 90%. The advantages of this approachinclude:

-   -   High efficiency (˜90% coil to coil).    -   Low ringing oscillation and EMI.    -   Simplicity and low cost.    -   Lower FET source-drain voltage swing allowing use of a larger        selection of FETs.

In many applications, it is also desired that the pad and the receiverare arranged so that the pad does not emit power unless the receiver isnearby.

FIG. 10 and FIG. 11 show circuit diagrams in accordance with anembodiment. In addition to high efficiency, one method that is requiredfor minimizing EMI and maintaining high overall efficiency is theability to recognize the presence of a receiver nearby, and then turningon the pad only when appropriate. Two methods for this are describedbelow.

As shown in FIG. 10, in accordance with one embodiment, the pad circuit260 incorporates a micro control unit (MCU1) 266 that can enable ordisable the FET driver 268. The MCU1 receives input from another sensormechanism that will provide information that it can then use to decidewhether a device is nearby, what voltage the device requires, and/or toauthenticate the device to be charged or powered.

One of the sensor mechanisms for this information are through the use ofan RFID reader 280 that can detect an RFID tag of circuit and antenna inthe receiver (i.e. device or battery to be charged or powered). Theinformation on the tag can be detected to identify the voltage in thereceiver required and to authenticate the circuit to be genuine or underlicense. The information on the tag can be encrypted to provide furthersecurity. Once a device or battery containing the tag is nearby the pad,the RFID reader can be activated, can read the information on the tagmemory, and compare with a table to determine authenticity/voltagerequired or other info. This information table can also reside on theMCU1 memory. Once the information is read and verified, the MCU1 canenable the FET driver to start driving the coil on the pad and toenergize the receiver.

In another embodiment the MCU1 relies on a clock 270 to periodicallystart the FET driver. The current through the FET driver is monitoredthrough a current sensor 264. Several methods can be implemented withthis implementation, including for example:

-   -   A small resistor can be placed in series with the FET to ground        contact. The voltage across this resistor can be measured by a        current sensor chip, such as a Linear Technology Current Sense        Amplifier part number LT1787.    -   A Hall sensor, such as a Sentron CSA-1A, that measures the        current from a wire running under it, can be placed on top of        the PCB line from the FET to the ground to measure the current        without any electrical connection to the circuit. The advantage        of this approach is that no extra resistor in series with this        portion of the circuit is necessary reducing the impedance.    -   Other techniques may be used to measure the current.    -   A Hall sensor or a Reed switch can sense a magnetic field. If a        small magnet is placed inside the receiver unit of the system, a        Hall sensor or Reed switch can be used to sense presence of the        magnet and can be used as a signal to start the FET.    -   Other capacitance, optical, magnetic, or weight, etc. sensors        can be incorporated to sense the presence of a secondary or        receiver and to begin the energy transfer process.

FIG. 11 shows a figure of a circuit diagram 290 in accordance with anembodiment. In accordance with an embodiment, the MCU1 can periodicallystart the FET driver. If there is a receiver nearby, it can power thecircuit. The regulator 296, or another memory chip in the circuit can beprogrammed so that on power-up, it draws current in a pre-programmedmanner. An example is the integration of an RFID transponder chip in thepath, such as ATMEL e5530 or another inexpensive microcontroller (shownhere as MCU2 294), that upon power-up modulates the current in thereceiver that can then be detected as current modulation in the primary.As with the previous example, other sensors, such as an RFID antenna 292can also be used to provide positional and other information.

FIG. 12 shows a figure of a power transfer chart 300 in accordance withan embodiment, illustrating transferred power as a function of offsetbetween coils.

Efficiency Enhancements in Coil Layout

An important aspect of power transfer efficiency relates to thealignment of coils with respect to each other.

FIG. 13 and FIG. 14 show figures of a coil layout in accordance with anembodiment. If position independence is required, the pad PCB can bepatterned with a coil pattern to cover the full area. FIG. 13 shows apad type charger or power supply 310 including a layer of coils 312 withminimal spacing 314 between the coils. Each coil has a center 316associated with it. In accordance with an embodiment, the power transferfor a 1.25″ diameter coil as the center of the receiver is offset fromthe center of primary. The power drops off to 25% of the maximum valuewhen the two coils are offset by a coil radius. As described above, inorder to better keep the coils aligned, use of magnets centered on theprimary and the receiver coil can provide an automatic method ofbringing the two parts into alignment.

In order to produce uniform fields, a number of coils around thereceiver coil will typically need to be turned on to produce a field.However, with such a pattern, if a receiver coil is placed in betweentwo primary coils, the voltage is still not optimized. Research hasshown that to obtain uniform fields, three layers of coil patternsoffset with respect to each other are required.

FIG. 14 shows a pad-type charger 320 with two of the three layers 322,324 required to achieve position independent magnetic field pattern. Fora receiver placed at the center of the circle, all the coils nearby (inand around the circle 328) will need to be turned on to achieve auniform field in the desired location 326. While this approach solvesthe offset issue and can be used to provide position independence, itdoes not produce high transfer efficiency. The reason is that ten ormore coils have to be turned on near the receiver center to create theuniform field in that area, which in turn leads to inefficient powertransfer.

Efficiency Enhancements through Independent Coil Movement

In accordance with some embodiments, techniques are included to providehigh transfer efficiency while maintaining position independence.

FIG. 15 shows a figure of a charging pad with multiple coils inaccordance with an embodiment. The area of the pad 330 is divided into aplurality of, or multiple segments 332, that are bounded 336 by a wallor physical barrier, or simply some tethering means with no physicalwalls but that otherwise restrict movement to within the segment. Thecoils 334 are mounted such that they can move laterally, or float,within the area of their segments while continuing to be connected tothe drive electronics placed on the edges of the area. In accordancewith an embodiment, the floating coils and the drive circuit aresandwiched between thin upper and lower cover layers that act to allowthe coils lateral movement while limiting vertical movement. When areceiver coil is placed on the pad, the pad senses the position of thereceiver coil and moves the coils to the right position to optimizepower transfer.

FIG. 16 shows a figure of a charging pad with movable coils inaccordance with an embodiment. When the mobile device, for example acell phone 340, or a battery is placed on the pad 330, the nearest coilmoves 342 within its segment to better orient itself with the mobiledevice or battery. In accordance with one embodiment, the method usedfor achieving this is by attaching a magnet to the bottom center of eachcoil in the pad. A matching magnet at the center of the receiver coilattracts the primary magnet nearby and centers it automatically withrespect to the receiver coil.

In accordance with an embodiment, each coil in this configuration can besuspended by the wires carrying power to the coil or by a separatewire/spring or by another mechanism so that each coil can move freely inthe plane of the pad while it can receive power from an individual orshared driving circuit. In order to facilitate movement, the surface ofthe coils or the bottom surface of the top layer for the base unit (thearea where the coils move against) or both layers can be made smooth byuse of a low friction material, attachment of a low friction material,or lubrication. The wire/spring or current carrying mechanism describedabove can also be used to center each coil in an area at the center ofdesired movement sector for each coil. In this way, without a receivercoil in the vicinity, each coil in the base unit stays at the centrallocation of its sector and responds and moves to match a receiver coilwhen a device or battery is brought nearby. Overlap of movement betweenadjacent charger or power supply coils can be controlled by means oflimiting movement through limiting length of current carrying wires tothe coil, arrangement of the suspension, or spring, or placement ofdividing sectors, pillars or by any other mechanism.

In another embodiment, the pad will include a method for detecting thepresence of the mobile device, battery/receiver and taking appropriateaction to turn on the coil and/or to drive the coil with the appropriatepattern to generate the required voltage in the receiver. This can beachieved through incorporation of RFID, proximity sensor, currentsensor, etc. A sequence of events to enable position independence andautomatic pad turn-on can be:

-   -   Multiple movable coils are used to cover the pad surface area.    -   The coils in the pad are normally off and periodically powered        up sequentially to sense whether the receiver is nearby by        measuring the current through the primary coil. Alternatively,        proximity sensors under each section can sense the presence of a        magnet or change in capacitance or other parameter to know where        a device is placed. RFID techniques with localized antennas        under each section or such can also be used.    -   Once a device is identified as placed in a section, the pad can        interrogate the device through one of the processes described        earlier to authenticate and to understand its voltage/power,        etc. requirements.    -   The MCU1 unit uses the information received above to set the PWM        pattern which it will use to drive the FET drive to produce the        appropriate voltage in the receiver.    -   The board continues to ‘search’ for other devices on the pad by        scanning coils or using the RFID system, etc. and then turn on        other coils as appropriate.    -   The pad also uses monitoring to find out when and if the first        mobile device is removed from the pad, or when the end of charge        is reached.        Efficiency Enhancements in Coil Registration and Switching

In accordance with an embodiment, a global RFID system that can identifythe approach of a mobile device to the pad can be used to ‘wake up’ theboard. This can be followed by sequential polling of individual coils torecognize where the device is placed in a manner similar to describedabove. Other embodiments can be used to provide safeguards against falsecharging of objects placed on the base unit. It is known that a metalobject placed on coils such as the ones in the base of the charger orpower supply system will cause current to flow in the primary andtransfer power dissipated as heat to the metal object. In practicalsituations, this will cause placement of keys and other metal objects onthe base unit to trigger a start and to needlessly draw current from thebase unit coil and possibly lead to failure due to over-heating. Toavoid this situation, in embodiments such as described above, theswitching of voltage to the coil will not start unless an electronicdevice with a verifiable RFID tag is nearby thereby triggering thesequence of events for recognizing the appropriate coil to turn on andoperate. In an alternate geometry, the total system current orindividual coil current is monitored, and, if a sudden unexpected drawncurrent is noticed, measures to investigate further or to shut down theappropriate coil indefinitely or for a period of time or to indicate analarm is taken.

In another embodiment, the regulators or battery charging circuit inmobile devices or batteries, or the regulator in a receiver electronics,typically has a start voltage (such as 5 V) that is required to startthe charging process. Once the battery charge circuit detects thepresence of this voltage, it switches on and then proceeds to drawcurrent at a preset rate from the input to feed the battery forcharging. The battery charger circuits operate such that an under orover voltage at the start will prevent startup. Once the startup occurs,the voltage at the battery charger output is typically the voltage ofthe battery and depends on the state of charge, but is for example 4.4 Vto 3.7 V, or lower for Lithium-Ion batteries. With a wireless chargesystem such as described here, the voltage on the receiver is highlydependent on relative position of the primary and receiver coil as shownin FIG. 5. Since typically the start voltage of the battery charger iswithin a narrow range of the specified voltage, under-voltage andover-voltage in the receiver coil due to misalignment or other variationwill result in shutdown of the battery charger circuit.

Efficiency Enhancements through Coil Voltage Clamping

FIG. 17 shows a figure of a circuit diagram 350 in accordance with anembodiment. In accordance with one embodiment, a Zener diode 352 isincorporated to clamp the maximum voltage at the output of the receiverprior to the regulator or battery charger circuit, as shown in FIG. 17.Using a Zener allows more insensitivity to placement between the primaryand receiver coil while maintaining the ability to charge or power thedevice. For example, the drive pattern on the primary can be set so thatwhen the primary and receiver coil are aligned, the voltage on thereceiver is above the nominal voltage for the battery charger startup.For example, for a 5 V startup, the voltage at center can be set for 6or 7 volts. In this way, the Zener can be chosen to have an appropriatevalue (5 V) and clamp the voltage at this value at the input to thebattery charger unit while the coils are centered or mis-aligned. Oncethe battery charger starts operation after detection of the appropriatevoltage at the input, the battery charger circuitry will pull thevoltage at this point to the pre-programmed voltage or voltage of thebattery. In this way, the use of Zener diode enables less sensitivity toposition and other operational parameters in wireless chargers or powersupplies and is extremely useful.

Efficiency Enhancements through Coil Stacking

FIG. 18 shows an illustration of a means of stacking coils, inaccordance with an embodiment. In accordance with an embodiment, toachieve higher flux densities, a coil is constructed with two or morelayers, for example by using two or more layers of printed circuitboard. Multiple layer boards can be used to allow compact fabrication ofhigh flux density coils. By altering the dimensions of the coil in eachlayer (including the thickness, width, and number of turns) and bystacking multiple layers, the resistance, inductance, flux density, andcoupling efficiency for the coils can be adjusted so as to be optimizedfor a particular application.

In accordance with an embodiment, a transformer comprising two PCB coilsseparated by a distance has many parameters that are defined by thedesign of the coil, including:

R1 is the primary winding resistance,

R′2 is the secondary (in the receiver) winding resistance referred tothe primary,

RL is the resistive load,

Llk1 is the primary leakage inductance,

L′lk2 is the secondary leakage inductance referred to the primary,

LM1 is the primary mutual inductance,

C1 is the primary winding capacitance,

C′2 is the capacitance in the secondary winding referred to the primary,

C12 is the capacitance between primary and secondary windings, and

n is the turns ratio.

In accordance with the embodiment shown in FIG. 18, a multi-layer PCBcoil 356 is created in separate PCB layers 357, which are then connected358, and manufactured together via common techniques used in PCBfabrication, for example by use of a via or contacts. The resultingoverall stack is a thin multi-layer PCB that contains many turns of thecoil. In this way, wide coils (low resistance) can be used, while theoverall width of the coil is not increased. This technique can beparticularly useful for cases where small x-y coil dimensions aredesired, and can be used to create higher flux densities and moreefficient power transfer.

Efficiency Enhancements through Coil Shape and Materials

In accordance with an embodiment, the system can use a non-ferritematerial for both the primary and the secondary (receiver) coils. Forexample, the coils can be made of copper material that is sputtered,deposited, or formed onto a printed circuit board (PCB), as describedabove. As also described above the coils can be formed in any number ofdifferent shapes, including, for example, flat or planar hexagonalshapes, or spirals. The coils can also be distributed in layers ofcoils, spirals, and other various shapes.

One of the advantages of using a non-ferrite or non ferromagneticmaterial for the primary and secondary (receiver) is that the coils canbe made much flatter and thinner than a ferrite coil. Additionally,non-ferrite coils can be made to have a lower inductance than acomparable coil made from a ferrite material (the inductance is on theorder of 1 micro Henry, although the actual value will vary depending onthe frequency of the voltage applied to the coil). The non-ferritenature effectively eliminates hysteresis in the coil, and allows thesystem to be switched on and off more rapidly, and with less energystorage artifacts.

Variations in Coil Circuitry

In accordance with some embodiments, an inductance-capacitance (oftenreferred to as an LC or “tank capacitor”) circuit can be used to providea range of power outputs to approximately suit the intended application.For example, the circuit can be optimized to suit either low-powerapplications, or high-power applications.

Depending on the particular intended application, the original capacitor(referred to herein as a “timing capacitor”) in the circuit design canbe removed and/or replaced with a different value of capacitor to obtaina different overall level of power output. From a manufacturingperspective this is a relatively simple and inexpensive procedure. Thistechnique can also be used to easily manufacture different charger orpad embodiments for different end-user applications, in that themajority of the pad components can be designed to be common to each paddesign, with the primary difference being the value for a singlecapacitor. This single capacitor can then be specified or changed duringthe manufacturing process. Although the timing capacitor can be used toadjust the system for, e.g. high-power or low-power applications, thefinal power output as it is received at the mobile device can befine-tuned using additional techniques and features such as thosedescribed in further detail below.

Coil Waveform Generation

In accordance with an embodiment, a half-phase electrical waveform isused to charge the tank circuit, and to subsequently provide inductivepower to the receiver coil in the mobile device. Unlike a full-phasewaveform, the half-phase waveform can be used with a zero-crossing powersupply. In accordance with this embodiment, when the transistor in theprimary coil is first turned on, electrical current passes through theprimary coil and the transistor to ground. When the transistor is turnedoff, the voltage level at the transistor swings high (anywhere fromtwice, to many times the value of the input voltage). This is thestandard oscillation behavior of an inductor. When the current falls tozero the transistor is turned on again, and the process is repeated.

Many traditional transformer designs do not use half-phase waveforms,and instead use a non-zero-crossing design, since their ferrite coreacts like a capacitor and stores energy during the off phase, whichresults in large losses in power efficiency if zero-crossing was used.However, in accordance with an embodiment, the use of non-ferrite coils,coupled with lower power (on the order of 2 Watts) allows for suitableefficiency with a half-phase and a zero-crossing circuit.

Furthermore, in accordance with some embodiments the half-phase waveformcan be designed to have an exponential or curved shape, rather than anabrupt shape, so that higher frequency emissions are reduced. Thesehigher frequency emissions might otherwise cause problems with portableand other devices, or conflict with federal communications regulationsthat prohibit high frequency emissions in consumer electrical devices.

Automatic Voltage Setting

In accordance with some embodiments, the system can include additionalcircuits, components, features, and techniques, which performspecialized tasks, such as mobile device identification, and automaticvoltage or power-setting for different devices. As described above,although the timing capacitor can be replaced to modify the circuitfrequency and the resulting output voltage of the system, this is not apractical solution for allowing a consumer to modify the voltage, or tomodify the voltage to suit the particular requirements of individualmobile devices. In practice the timing capacitor can be used to providea particular range of output power (i.e. high power applications; or lowpower applications). Additional techniques are then used to adjust thepower for a particular device. This is particularly important when thecharger or the pad is designed to power or charge multiple differentdevices simultaneously, since each of those different devices may havedifferent power and voltage requirements. In accordance with variousembodiments, different features can be used to support this, including:

-   -   Hardwiring the receiver coil to take the voltage requirements of        its device into account, and to use the appropriate dimensions        to receive the correct voltage for that device. However, while        this approach works to adjust the voltage for that device, it is        by its nature hard-wired and does not provide much flexibility        to adjust the voltage for interoperability between different        devices and different chargers or power supplies.    -   Use of dynamic programming to obtain a different voltage. In        accordance with this embodiment, if the timing capacitance is        known, then the frequency of the circuit can be adjusted to        produce the required output voltage.    -   In a zero-switching circuit, clipping can be used to tune the        voltage. This can include turning the circuit on, then allowing        it to turn off but clipping the waveform earlier, and then        turning it on again. The process is then repeated. The clipping        may be less efficient than unclipped switching, but can be used        to tune the voltage.

When used with the above capacitor-based techniques, the choice oftiming capacitor can be used to determine the overall range of thecharger, power supply, or pad (for example, whether it is best suitedfor low power, or for high power applications). The additional featurescan then be used to fine-tune the frequency and the output voltage. Inaccordance with some embodiments, additional features can be used toimprove efficiency and to add functionality.

As described above, in accordance with one embodiment, the pad circuit260 incorporates a micro control unit (MCU) 266 that can enable ordisable the FET driver 268. The MCU receives input from another sensormechanism that will provide information that it can then use to decidewhether a device is nearby, what voltage the device requires, and/or toauthenticate the device to be charged. The communicated feedback fromthe receiver to primary can be used by the primary to, for example,adjust the frequency, or to otherwise alter the output voltage to thatreceiver, using the frequency/output characteristics described above.Some traditional transformer designs use a third coil to provide ameasure of feedback. However the use of an MCU as described hereineliminates the need for such extra coil feedback devices.

Also as described above, in accordance with one embodiment, a Zenerdiode 352 is incorporated to clamp the maximum voltage at the output ofthe receiver prior to the regulator or battery charger circuit. In eachof the feedback designs described above, the actual communicationbetween the receiver and the primary as to voltage requirements can beof open loop design, or of closed loop design. In an open loop design,the charging device, pad or power source provides the power to theprimary, which is then inductively transferred to the receiver and themobile device or battery other device to be charged. The primary itselfdetermines how much power should be received at the receiver. In aclosed loop design, such as in a switching mode power supply, thedevice/receiver communicates information back to the primary, and thenthe primary determines how much power should be sent to the receiver.

Device Identification and Verification

FIG. 19 shows a figure of a circuit diagram 400 for identificationverification in accordance with an embodiment. In accordance with anembodiment, the circuit design can be used to ensure a device is valid,i.e. authorized to be used with the charger, power supply or pad. Theinformation can also be used as part of an open-loop or closed-loopdesign to set the voltage for the device. In operation, the primarycircuit is first turned on. An initial signal is generated as thecircuit induces power in the receiver. This information is quicklycompared with a number or value stored in the MCU, and is used todetermine whether the mobile device (or the receiver associated withthat mobile device or battery) is valid for operation with the baseunit, charger, power supply, or charging pad. In addition to validationthe information can similarly be used to set the charging voltage forthe receiver, battery, or mobile device.

FIG. 20 shows a figure of a circuit diagram 420 for bidirectionalcommunication in accordance with an embodiment. As shown in FIG. 20, inaccordance with an embodiment the charger or power supply or primary caninclude means for communication with the receiver, battery, or mobiledevice, including for example radio frequency (RF) or other means ofcommunication.

FIG. 21 shows a figure of a circuit diagram 440 for output controller inaccordance with an embodiment. As shown in FIG. 21, in accordance withan embodiment the output controller in the receiver waits until power issufficient, and then turns the power on to the mobile device or battery.

FIG. 22 shows a figure of a circuit diagram 480 for receiver withregulator or charge management circuit in accordance with an embodiment.As shown in FIG. 22, in accordance with an embodiment the receiverincludes a regulator for regulating the voltage.

FIG. 23 shows a figure of a circuit diagram 500 for MCU regulation inaccordance with an embodiment. As shown in FIG. 23, in accordance withan embodiment the MCU can provide the voltage regulation.

FIG. 24 shows a figure of a circuit diagram 540 for unidirectionalcommunication and data transfer in accordance with an embodiment. Asshown in FIG. 24, in accordance with an embodiment the receiver caninclude a means of transferring data to the mobile device to which it iscoupled.

FIG. 25 shows a figure of a circuit diagram 560 for time-basedregulation in accordance with an embodiment.

Zero Voltage Switching

In accordance with some embodiments, the system can use a technique suchas Zero Voltage Switching (ZVS) to provide more efficient power transferand power supply control. These techniques can also be used to providemore efficient regulation for power transfer between coils of smallinduction value, such as those created by spiral patterns in PCBs,stamped metal coils, and low number of turns wound wire coils. Inswitching mode power supplies used today, the common geometries used areboost buck, flyback, boost, or a variation of these types. In most ofthese geometries, the input voltage is switched rapidly by a transistorsuch as a FET and the energy is transferred across a transformer to aload. In accordance with an embodiment, by adjusting the duty cycle ofthe switching circuit, regulation of transferred power is achieved.

FIG. 26 shows a high level view of a flyback power supply geometry 580in accordance with an embodiment. During the time that the FET isclosed, the current through the primary coil stores energy in this coiland during the period that the FET is open, this energy is transferredto the secondary (receiver) coil and into the load. The energy stored inthe coil is directly proportional to the inductance of the coil andvalues of several hundred Henry are typical for 10's or 100's of Wattsof power supply power.

In contrast, Printed Circuit Board Coils (PCBC's) are typically spiralcircular, rectangular, or other shape coils that are printed on rigid orflexible PCB material or stamped out of sheets of copper or by othermethods where the coil or transformer in a power supply is primarilyflat and takes very little space. Two of these coils placed with adistance between them (such as on both sides of a PCB material) or withan air or material gap (such as in wireless power applications where acharger transmits power to a receiver in an electronic or electricdevice that can be separated or removed from the charger) can be used toform a transformer such as the one shown in FIG. 26. Switching of thesecoils at high frequency (˜1 MHz depending on the coil geometry and size)can transfer power across an air or material gap and an efficient powersupply with a very small transformer can be developed. Uses of suchcompact coils for wireless powering of mobile devices such as mobilephones and MP3 players have been demonstrated. However, many priortechniques used a laboratory power supply to provide a sinusoidal orsimilar voltage to the primary coil and study the transferred power,rather than a compact efficient circuit for a power supply.

In accordance with a ZVS geometry embodiment, a capacitor is added tothe circuit so that in the switch OFF position, the capacitor and thecoil inductor create a resonant circuit. During the switch ON time,current passes through the inductor while the voltage across thecapacitor is zero. During the period where the switch is turned off, thevoltage across the capacitor rises to a maximum value of twice the inputvoltage and then resonates back to zero. A characteristic of thisgeometry is that the switch is closed exactly when this voltage arrivesback to zero (hence the name Zero Voltage Switching), thereby minimizingpower usage and achieving high efficiencies. Some of the benefits ofthis geometry include: High efficiency and ‘Loss-less’ transitions;Reduced EMI/EMC due to soft switching and use of sinusoids rather thansquare waves; Peak current is not higher than square wave switching; andRelatively simple control and regulation. In addition, this geometry canwork very efficiently with low inductance values and is therefore bettersuited for the PCBC applications. In accordance with various embodimentsthe geometry can be configured to operate in various topologies, forexample buck, boost, buck-boost, and flyback.

Some embodiments provide more efficient power transfer and power supplycontrol and regulation for power transfer between coils of smallinduction value such as created by spiral patterns in PCBs, stampedmetal coils, low number of turns wound wire coils, etc. In addition,typically, magnetic cores are not used if the coils are driven at highfrequency. For a spiral coil, the inductance of a coil is given by:

$L = \frac{r^{2}N^{2}}{( {{2r} + {2.8d}} ) \times 10^{5}}$Where

-   -   L=inductance (H)    -   r=mean radius of coil (m)    -   N=number of turns    -   d=depth of coil (outer radius minus inner radius) (m)

For example, for a coil of 10 turns, an outer radius of 15 mm, and innerradius of zero, then L=1 H. While larger values can be obtained byincreasing the number of turns or stacking a number of coils verticallyand connecting them in series, this larger induction comes at the priceof increased resistance and therefore loss in the inductor.

Spiral coils printed on PCBs without use of any magnetic core canprovide high power transmission efficiency if operated at highfrequency. An analogous method to the above technique is one referred toas Zero Current Switching (ZCS). ZCS operates by similar principles;however switching is done during zero current passing through the switchthereby achieving low switching losses. In the following discussion, ZVSswitching is generally discussed; however, the ZCS geometry can equallybe applied to the following. In accordance with some embodiments,methods are described for achieving and optimizing high power transferwith such small and/or thin coils with low induction values and describeseveral techniques for control and regulation of this power in realworld power applications. While this technology is generally describedfor any type of power supply using such inductors, in accordance with aparticular embodiment the two coils in the transformer are separated,with the primary being in an inductive charger and the receiver embeddedin a device, battery, casing, skin, or other part of an electronic orelectric device. In this case, a wireless charger or power supply can becreated which is especially useful for charging or powering mobileelectronic or electric devices or batteries.

The advantages of use of ZVS geometry in general, and in particular forcoils with small inductance and no magnetic cores, has been describedabove. However, another important aspect of power supply design is theControl and Regulation Circuitry that is implemented. Regulation of thepower to a load can be achieved by a linear or switching regulator atthe output stage. However, if the regulation of the power is achieved inthis way and constant power is supplied from the primary coil, underlight load conditions (such as when a battery is fully charged or adevice is on stand-by, then the power generated and transmitted by theprimary is mostly wasted leading to a low efficiency power supply. Abetter solution is achieved by adjusting the power into the primary coilunder different load conditions, to maintain high efficiency duringdifferent load conditions or battery charging stages.

In accordance with an embodiment, such control of output power in a ZVSpower supply can be achieved by changing the frequency of the operation.In this embodiment, the output power is inversely proportional to theoperating frequency and control can be achieved by an appropriatecontrol circuit.

FIG. 27 shows how the output voltage to the load is monitored and withchanges in the load condition, a chip or a Micro Controller Unit (MCU)varies the frequency or the duty cycle of the FET driver to achieveoptimum operation and controlled output voltage with a changing load. Asshown in FIG. 27, a digital control 600 for operation is shown. However,analog operation can also be achieved and may be simpler and faster inresponse time to load changes and preferable in some applications. Inthe implementation shown, the primary (Control Circuit, Clock, FETDriver, FET, primary coil, etc.) and the receiver (secondary coil,rectifier, capacitor, other circuitry, etc.) are able to communicatethrough a wired connection.

Switching Mode Power Supply with Wireless Communication

In accordance with an embodiment that includes a charger or power supplywherein the charger or power supply and the receiver are separable fromeach other (wireless or inductive charging or supply of power todevices), the charger or power supply can contain the basic control andswitching functions while the receiver contains the rectifier diode andcapacitor for smoothing of the output voltage and additional circuitry.In this embodiment the two parts need to communicate with each otherwirelessly.

FIG. 28 shows an implementation of a more sophisticated charger or powersupply. According to this embodiment, where the primary stage and thesecondary (receiver) stage communicate wirelessly. In the geometry shownin FIG. 28, a digital control scheme is implemented. The primary(charger or power supply) 620 is controlled by a Micro Control Unit(MCU1) that receives signals from a Current Sensor in series with thecoil. The communication between the charger and the receiver 630 isachieved through the same coil as the power transfer. However, thesefunctions can be separated.

In the geometry shown, the secondary (receiver) contains circuitry thatenables this part to modulate the load as seen by the primary. Inaccordance with an embodiment this is achieved through modulation ofswitch Q2 by an MCU2 in the receiver. This can be a very smallProgrammable IC (PIC) and can easily fit into very small form factors.As the primary charger or power supply sends power to the secondaryreceiver, the circuit in the receiver turns on. The power received isrectified and filtered by rectifier D1 and Capacitor C2 respectively.Since MCU2 requires constant voltage input at all times, a small, lowcurrent regulator (Voltage Regulator) for powering MCU2 only isincorporated. This can be a linear or switching regulator. Since thepower usage of MCU2 is very small and the unit can also be put intohibernation between tasks, use of this regulator does not affect theoverall efficiency much. The output of the rectified stage is input to adevice or Charge Management IC for the case of a battery chargerconfiguration. This Charge Management IC is integrated into mostOriginal Equipment Manufacturer (OEM) mobile devices that operate byrechargeable batteries or can be integrated into or on a rechargeablebattery to directly charge the battery when the battery is in proximityto the charger. The Charge Management IC typically, for a fully drainedbattery, will pass on the maximum input current to the battery to enablerapid charging when the battery is at low voltage. This presents a lowimpedance load to the power supply circuit and requires the power supplyto sustain the voltage at the required value while supplying thecurrent. The Charge Management IC is in communication with the MCU2which also monitors the output voltage (Vout) and tries to maintain thisVout within a pre-programmed range. This is achieved by MCU2 sending adigital signal to Q2 to modulate the switch. This modulation is prior tothe rectifier stage and is at high frequency so the rectified andsmoothed Vout is not affected. However, this modulation of the impedanceof the secondary stage affects the current through the primary coilstage and can be easily detected by the Current Sense circuit in theprimary.

In accordance with an embodiment the Current Sense circuit can comprisea small resistor in parallel to a voltage amplifier, a Hall sensor, etc.The output of the Current Sensor is connected to MCU1 and the digitalsequence is detected by an A/D converter. The firmware in MCU1determines whether the output voltage is too high or too low and thenexecutes the appropriate step to adjust accordingly by sending a signalto a clock to adjust the frequency of the FET drive to bring the outputof the power supply to within acceptable range. Higher drive frequencycorresponds to lower output power by shortening the time for integrationof power in the resonant ZVS cycle and lower frequency corresponds tohigher output power.

In accordance with an embodiment, one method for implementing thevariable frequency is to use a variable frequency source whose outputfrequency changes with change in the voltage to its input. Using aprogrammable resistor and changing this resistor value by varying avoltage signal from MCU1, the frequency for driving FET 1 can bechanged. Other methods for achieving this change are also possible.

As an example of the method for control, in a typical application, theoperating frequency of the circuit can be 1-2 MHz and the datatransmission for control is at 14.4 kbits/sec. If the full output powerrange is achieved by moving the frequency in the 1.2-1.4 MHz, this rangeis broken into 256 steps. In one implementation, the receiver sends adigital code corresponding to the output voltage and MCU1 compares thisto the earlier output voltage value and makes a determination aboutwhich direction and by how many steps to move the frequency. Thefrequency is then changed accordingly. In another implementation, MCU2sends one of 2 values corresponding to a voltage high or low condition.If the voltage is within range, MCU2 does not communicate with theprimary. When a voltage high signal is received, MCU1, takes apre-determined step towards higher frequency to lower the output powerand the process is repeated until output voltage is within requiredrange. A voltage low signal has the opposite effect. Many variations ofthese basic methods are possible to allow rapid, efficient locking ofthe output voltage. Proportional-Integral-Derivative (PID) techniques,etc. can also be used. Depending on the geometry, the circuit may alsouse a switch Q3 in series with the load. This optional switch may beopened during communication to create a better signal to noise ratio.Since communication occurs in several msec, opening and closing Q3rapidly does not have a large impact on charging time of a load batterythat can be in many hours.

In accordance with an embodiment, as the battery charges and itsterminal voltage rises, the Charge Management IC throttles the incomingcurrent back, and switches to a mode where the voltage across thebattery terminal is maintained at or near its final value. The supplywill sense a higher output impedance and MCU2 and MCU1 work in concertto keep the output within range throughout the charging cycle. At theend of the charge cycle, the Charge Management IC can signal end ofcharge cycle to MCU2 which sends a pre-determined code to MCU1 to shutdown the charger, move to hibernation mode or take some otherpre-determined step.

It is important to note that, in the embodiment, the voltage regulatorin the receiver does not regulate the output voltage to the load itself.If the regulator was performing this function, then the control andregulation described here would not be necessary. However, the overallsystem efficiency is much lower and, with a constant power going intothe receiver, some fraction of this power is wasted as the batteryreached a full charge or as the load became lighter and less power wasrequired. This wasted energy can heat up the receiver, the load, or thedevice battery depending on the geometry. All of these cases areundesirable. In the geometry described here, the primary can in thesecases adjust to send less power to the receiver, thereby maintaininghigh efficiency regardless of load condition.

Verification and Data Transmission

In accordance with an embodiment, the digital transmission processdescribed here is bi-directional, and can be used for verificationprocess at start of charge or power transfer to ensure that the rightkind of device is present and about to be charged, or to inform thecharger or power supply about the voltage/power requirements of thedevice or battery to be charged or powered. In accordance with anembodiment, this bi-directional data transfer can also be used foractual data communication between a device and a charger or powersupply. For example, the charger or power supply can be powered by theUSB outlet of a laptop and simultaneously receive data from the laptopto be transferred to a mobile device. When a mobile device or battery ison the charger or power supply, it can be charged or powered, and itsdata can also be synchronized simultaneously through this channel.

Extension to other Geometries

While the above discussion has focused on one implementation of thecontrol with a Zero Voltage Switching power supply, the basic conceptsfor the control, verification, and data transmission are applicable toother geometries and topologies, and can be implemented in a similarmanner. In accordance with some embodiments, the Charge ManagementCircuit is optional and is only used when a battery is present at theload. For example, as shown in FIG. 28, If Vout is used to directlyoperate a load, the Charge Management Circuit is not used and Vout isdirectly connected to the load.

Fully Regulated Switching Mode Supply with Wireless Communication

FIG. 28, described above, shows the basic building blocks for adigitally controlled wireless control circuit for a Zero VoltageSwitching (ZVS) circuit were described. The geometry shown in FIG. 28can regulate the output power through a wide range. However, as abattery charges or the load condition changes to require very low outputpowers, the accuracy required for control of the Vout may require manyfiner steps or not be possible with the geometry of FIG. 28 alone.

FIG. 29 shows an embodiment that includes an enhancement that can beused to address the ZVS issue.

In the fully regulated power supply shown in FIG. 29, a voltageregulator (Voltage Regulator 1) that can switch the input voltagebetween 2 values or more is used. In normal operation, Q2 is closed andthe Voltage Regulator 1 is shut down though its enable pin. Therefore,the input voltage is directly available for the Coil L1 and is regulatedas described earlier. However, if the output requires extremely lowpowers (such as end of charge stage for batteries), and the chargerdetermines that a switch to a different range is required, Q2 is opened,and Voltage Regulator 1 is switched on to change the input to Coil 1 toa lower voltage value. Regulation is maintained at this range byshifting to the appropriate frequency to achieve required output power.For example, if Vin is 5 V, this lower voltage level may be 3 V.Multiple voltage levels are also possible.

Since for most cases, and in high power conditions, Q2 is open andVoltage Regulator 1 is turned off, high overall system efficiency can beachieved. Only during the lowest current conditions, the input voltageis changed by switching this Voltage Regulator 1 on and regulating atthis level. Depending on the type of regulator used, some efficiencyloss can be expected in this regime. However, this occurs at very lowoutput power levels only. Voltage Regulator 1 can be a high efficiencySwitching DC-DC supply or a lower frequency, less complicated and lesscostly linear regulator depending on efficiency/cost trade-offs.

Regulated Switching Mode Power Supply with Opto-Coupler Feedback

The geometries described above use a digital method for transmission ofinformation between a primary and receiver circuit. However, in somecases, the load changes instantaneously. Examples are when in a laptopcomputer, the screen or the hard drive start or shut down, etc. Tohandle these cases, the feedback loop has to be extremely fast to avoidhaving severe and rapid voltage overshoots and undershoots. This becomesespecially important for high power applications.

FIG. 30 shows an embodiment in which instead of a digital feedbackcircuit, an analog circuit based on coupling between an LED and a lightdetector can be used.

In this case, the output voltage, Vout is continuously compared to areference voltage and the intensity of light from a diode changesrapidly in proportion to the voltage value. A detector in the chargerstage provides a voltage value to a frequency controller that controlsthe FET drive. An MCU in the charger, MCU1 also monitors the process andcan switch on an optional lower voltage input to the primary coil(through Q2 and Voltage Regulator) if necessary. It can also sense theend of charge or perform verification or other tasks.

In some embodiments a high power completely wireless inductive chargerfor a laptop requiring up to 90 W continuously can be implemented withthis scheme. In accordance with an embodiment the transformer coils arePCB spiral coils that have 4″ or more diameters and comprise 7 turnswith a total inductance of 1 micro Henry. The rapid response time of theanalog circuit allows maintaining of the output voltage with rapidswings in the load. The charger or power supply comprises a pad wherethe charger or power supply circuitry and a flat spiral PCB coil areintegrated into and the receiver comprises circuitry and a similar coilintegrated into the bottom of a laptop. The optical components aremounted such that the light from the transmitter is detected by thereceiver in the charger or power supply.

Digital communication through the optical parts is also possible toachieve this result, but requires a higher bandwidth and high speedprocessing.

It will be evident that these features, or any other geometry describedhere, can be combined to achieve the desired results. For example, whilethe control process for regulation may be through the opto-couplerfeedback described here, a separate digital data link through the coilcan be established for data transmission or verification of the charger,power supply, or vice versa.

Regulated Switching Mode Power Supply with Isolated Transformer Feedback

In accordance with an embodiment, another geometry for the regulationuses a similar analog feedback technique with the feedback informationbeing transferred through a separate isolated transformer.

FIG. 31 shows an embodiment in which the opto-coupler is replaced by aVoltage Controlled Oscillator (VCO) and FET and in the primary, thesignal is sent to adjust a frequency controller to provide optimumoutput voltage. An optional voltage regulator and switch Q2 can also beused to provide precise control at low output powers. Similarly, thiscommunication can be implemented digitally, and also requires a highbandwidth to allow for rapid response. Since the circuit in FIG. 31 iscompletely wireless and does not require optical components, it may bepreferable in cases where an optically transmissive window in thecharger or power supply or the receiver may not be possible.

Regulated Switching Mode Power Supply with RF Feedback Regulation

In accordance with another embodiment, the information between thecharger and the receiver can be exchanged through a wireless link in thetwo parts. The advantage with this embodiment compared to the opticalcase is that the two parts do not need to be optically transmissive. Inaddition, compared to the earlier-described versions (optical andthrough a transformer), the relative alignment is not as important.However, in most practical application, the charger or power supply andthe receiver coil will be aligned for power transfer, so an alignment ofsome degree will occur and with the right geometry, can enabletransformer or optical feedback alignment and regulation to beimplemented.

FIG. 32 shows an embodiment in which the wireless link can be analog ordigital (requires higher bandwidth and complexity) or can be integratedinto the device to take advantage of existing wireless links in thedevice (Bluetooth, WiFi, Wireless USB, WiMax, etc.).

FIG. 33 shows a basic schematic for an inductive single coil chargingsystem in accordance with an embodiment. As shown therein, the coilinductor in the charger pad is switched by Switch T which is typically aFET transistor. A capacitor in parallel with the FET may be used toimprove performance. The receiver in the right hand side comprises asimilar coil, rectifying diode, and a capacitor to provide DC output toa load R_(L).

FIG. 34 shows the main components of a more advanced wirelesspower/charging system. Charge Management IC in the receiver alsocontrols the charging of the battery to ensure appropriate charging. TheMCU1 and current sense chips in the charger and MCU2 can providebi-directional communication between the charger or power supply and thereceiver for optimum charging or supply of power. The optional voltageregulator in the receiver is used to provide a constant low currentvoltage to MCU2 and is not regulating the power into the battery. TheReceiver is integrated into or on a mobile or electronic device or arechargeable battery. Points A, B and C are described later and can beused for placement of switching circuits. Q3 is a switch that candisconnect the battery during communication for higher signal to noiseratio and is optional.

An embodiment of the system incorporates a MicroControl Unit (MCU1) thatcan enable or disable the FET driver. This system also uses a ChargeManagement IC in the receiver which controls the charging of the batteryto ensure appropriate charging profile is followed and the battery isnot overcharged. Most mobile devices today already include a ChargeManagement IC in their power circuit between the input power jack andthe rechargeable battery of the device to control charging of theirinternal battery. This chip can be incorporated into the receivercircuitry to enable a battery to directly receive power from aninductive source as shown in FIG. 34.

FIG. 34 also shows a Zener diode (Z1) incorporated at the receiver. ThisZener is used to ensure that the output voltage from the rectifier doesnot exceed a pre-determined value. In some instances this may beimportant, since the output of the receiver is fed into a ChargeManagement IC that may have a finite turn-on time. At the beginning ofcharging (when a device is placed on a pad first), the Charge ManagementIC may seem like a high impedance load. Without the Zener diode, such aload may cause the voltage the input to the Charge Management Circuit toincrease to high values, potentially exceeding its safe operatingconditions. A fast Zener diode can clamp the voltage under this or otherunusual conditions and may be incorporated into the receiver. Dependingon the architecture, other methods for avoiding such conditions may beincorporated. Incorporating a Zener Diode is an effective, andinexpensive method for dealing with these potential issues.

In accordance with an embodiment, the receiver may also incorporate avoltage regulator just to provide a constant voltage (or voltage in theacceptable range for operation) to MCU2. This voltage regulator justprovides the low power necessary for this and is not in the path of themain power going into the battery. Any power loss due to this regulatoris small, because it is very low power and does not affect the overallsystem efficiency much. It is mainly used to keep the MCU active duringstartup or other changes so the communication with charger or powersupply is maintained.

The MCU1 receives input from another sensor mechanism that providesinformation that it can use to decide whether a device or battery isnearby, what voltage the device or battery requires, and/or toauthenticate the device or battery to be charged or powered. Severalexamples of the mechanisms for providing this information are:

The MCU1 periodically starts the FET driver. The current through the FETis monitored through a current sensing method. The inductance of L1 ishighly dependent on the presence of objects nearby that affect itsmagnetic field. These objects include metallic objects or another nearbycoil such as L2. Switching L1 at high frequency (100 kHz to several MHz)through a Field Effect Transistor (FET) such as Q1, the value of currentbeing drawn is highly dependent on the L1 Value. This property can beused to sense the presence of nearby devices or batteries capable ofdrawing power and also to enable bi-directional communication ifdesired. Several methods for this are possible:

-   -   A small resistor can be placed in series with the FET to ground        contact. The voltage across this resistor can be measured by a        current sensor chip such as Linear Technology Current Sense        Amplifier part number LT1787.    -   A Hall sensor such as Sentron CSA-1A that measures the current        from a wire running under it can be placed on top of the PCB        line from the FET to the ground to measure the current without        any electrical connection to the circuit. The advantage of this        approach is that no extra resistor in series with this portion        of the circuit is necessary reducing the impedance.    -   Other techniques can be used to measure the current.    -   By monitoring the current and comparing it to a baseline        measurement taken at power up, and periodically with no devices        nearby, MCU1 can determine whether a device or battery is near        the coil and drawing power. This provides a first level        verification of an object capable of drawing power being nearby.        However, there may be a possibility of false starts with        metallic objects or wires in any electronic device or battery        drawing power. A second level of verification may be desirable.

To enable a more secure verification, in accordance with an embodimentthe MCU1 can periodically start the FET driver. If current is beingdrawn, MCU1 may activate the Q1 in a predetermined state (for example,this may be a low power state). This can provide a first levelindication that a receiver may be nearby. If there is a genuine receivernearby (versus, say, a metallic object, electronic device, or anon-approved receiver), the emitted power from L1 will power thereceiver circuit. The charge control circuit in the figure or anotherchip in the Receiver circuit can be pre-programmed so that on power-up,it draws current in a pre-programmed manner. An example of this is theintegration of the MCU2 and chip model number 10F220 Programmable IC byMicrochip Inc. or another inexpensive microcontroller that uponpower-up, executes a predetermined program that modulates the currentbeing drawn in the receiver in a predetermined code (which can beencrypted). This receiver modulation can be detected as a currentmodulation in the current through the L1 by the charger or power supplycurrent sensor in FIG. 34.

After the initial handshake and verification, the MCU1 and current sensechips in the charger or power supply and MCU2 can provide bi-directionalcommunication between the charger or power supply and the receiver foroptimum charging or supply of power. The system can also regulate thepower and voltage received at the Charge Control Circuit to insureovervoltage conditions do not occur. As shown in FIG. 34, switch Q3 is aswitch that can disconnect the battery during communication for highersignal to noise ratio and is optional.

If the handshake and verification between the charger or power supplyand the receiver is not successful, the MCU1 will assume that the devicedrawing power is not an appropriate receiver and will terminate poweringit. This process invalidates false starts due to objects beingaccidentally placed on the pad, and also provides protection againstcounterfeit or non approved receivers. An RFID, Near-Field Communication(NFC) or other wireless data transmission method reader that can detectan RFID, NFC, or other tag included with the receiver circuit andantenna (i.e. device or battery to be charged). The information on thetag can be detected to identify the voltage for the receiver required,and to authenticate the circuit to be genuine or under license.

The information on the tag can be encrypted to provide further security.Once a device containing the tag is near the charger or power supplypad, the tag reader is activated, the system reads the information onthe tag memory, and compares it with a table to determineauthenticity/voltage required or other info. In some embodiments, thisinformation table can also reside on the MCU1 memory. Once theinformation is read and verified, the MCU1 can enable the FET driver tostart driving the coil on the pad and to energize the receiver.

A Hall sensor or a Reed switch can sense a magnetic field. If a smallmagnet is placed inside the receiver unit of the system, a Hall sensoror Reed switch can be used to sense presence of the magnet and can beused as a signal to start the FET.

Other capacitance, optical, magnetic, or weight, etc. sensors can beincorporated to sense the presence of a receiver and to begin the energytransfer process.

The methods for verification and communication between the charger orpower supply and the receiver are provided above by way of example, andin accordance with various embodiments. In practice a combination or avariation on the above methods may be used. It will also be evident thatdifferent embodiments can use different verification techniques, inaddition to or instead of those described above, and variouscombinations of such.

Efficiency Enhancements through Lateral Offset Between Coils

FIG. 35 shows a typical experimental curve for power transferred andPower Transfer Efficiency through a pair of circular spiral coils as afunction of lateral offset between the center of the coils. The powertransferred is shown at the receiver after rectification and otherelectronics, and is the DC power available for charging/powering adevice. Power Transfer Efficiency is defined as the DC Power out fromthe receiver divided by DC power into the charger or power supplycircuit; so it includes any power consumed by the FET driver, the FET,rectifier diode, and other electronics. This efficiency includes alllosses (electronics, coil to coil losses, rectifier, etc.) and is a morepractical number for efficiency than the ratio of AC power out of areceiver coil to AC power into a charger or power supply coil commonlyused. It can be seen that very efficient power transfer efficiency canbe obtained with inductive methods. In accordance with the exampleshown, the coils can be identical and 1.25″ in diameter and comprise 10turns.

As can be seen from FIG. 35, for the coil geometries used here, at anoffset between the center of coils of half the radius, the powertransferred can be 75% of the maximum value. Improvements in flatness ofthe curve may be possible with changing the design of the coil tooverlap more of the field on the outer areas of the coil or by usinghybrid coils.

However, it is important to note that while the transferred powerdecreases with offset between the coil centers due to reduced overlap ofthe coil areas, the power transfer efficiency (ratio of DC power outfrom receiver to DC power into charger or power supply) remainsrelatively constant in the range of offset <3 r/4. This is a morecritical factor in design of an efficient system. If one assumes that asystem can be designed such that the coil offset is never larger thanr/2, then in a wireless charging or power transfer system, then, one candesign the system such that the power transferred at this maximumpossible offset is equal or greater than the maximum transferred powernecessary.

For example, if FIG. 35 represents the maximum power transfer possiblegiven the particular coil type, size, and geometry and the switchingcircuit (FET) and circuit design, then 3 W or more power can betransferred depending on the offset between the coils assuming that thecoil offset is always smaller or equal to r/2. For a power supplyapplication where regulated, constant power to a device is necessary,using regulation of the output power or a feedback to the charger orpower supply to change the frequency or duty cycle, etc. to keep thepower constant can insure that the received power to a device isindependent of the offset between the coils. For example in this case,using regulation, one can ensure that up to a maximum power of 3 W canbe provided to a load independent of coil offset (up to the maximumallowable offset—assumed to be r/2 here). In this case, the 3 W issufficient for most mobile devices (mobile phones, cameras, Bluetoothheadsets, etc.). Again, it is noted that the overall efficiency of thesystem remains high in all cases, since the offset (within the range ofpossible offset values) and regulation of the power (if it is performedat the charger or power supply by changing duty cycle, etc.) do not havea large impact on efficiency.

Position Independence using Layers

From the discussion above, one can achieve the goals of high efficiencyand position independence if a method is found wherein the offsetbetween the charger or power supply and receiver coils is always keptequal or less than r/2. In the case of hexagonal spirals with side=r,the maximal diameter is 2 r (similar to a circle with radius r). So fora given hexagon with side=r, the same relation holds. As describedherein, several methods of achieving this are proposed.

FIG. 36 shows an embodiment in which a coil mosaic is used to cover thesurface area of the pad. The circuitry can include means of sensing thepresence of a receiver coil to start the appropriate driver to providepower. The drive and sense circuits and other electronics are shown hereas components in the perimeter of the coil area but can be locatedanywhere. The approximate Effective Area is also shown. If the center ofa receiver coil is placed anywhere within the effective area, thereceiver will receive the specified power with only one appropriate coilin the charger or power supply activated.

In the geometry described here, each coil is driven by its own drivecircuit. A sensing mechanism senses the presence of a receiver coil ontop or close to a charger or power supply coil and starts the drivecircuit to power the appropriate coil. The sensing mechanism can be acurrent sense mechanism. Each coil drive circuit can periodically startdriving the coil at an appropriate frequency and a current sense circuitcan monitor the drawn current to sense when a receiver is nearby therebyaffecting the inductance of the charger or power supply coil. Drivingthe charger or power supply coil circuit at an appropriate frequencydetermined by the inductances of the charger or power supply andreceiver coils and the capacitance of the load, can provide very highsensitivity to this change in the inductance.

Additional verification can be obtained by exchanging a verificationcode through the coils or by exchange of information through a secondwireless data communication link (such as RFID, NFC, WiFi, etc.) betweenthe pad and the device(s) to be charged. The code exchange can alsoprovide information to the charger or power supply coil regarding thenecessary voltage, power, temperature, or other diagnostic informationfor achieving reliable charging.

The approximate Effective Area is shown in FIG. 36. Any point within theEffective Area shown has the property that a receiver coil placed withits center within this area is always within half a width or less of thecenter of at least one charger or power supply coil. If the system isdesigned such that moving the receiver coil within half the width of thecenter of any given activated coil provides at minimum the maximumoutput required (i.e. 3 W in the earlier example), the Effective Areahas the property that a receiver coil with its center anywhere withinthis area can receive the necessary maximum output power or more withonly one appropriate charger or power supply coil activated.

For the geometry shown in FIG. 36 comprising 75 hexagonal coils withside=r in 3 layers, the effective area is approximately 12 r wide and 6mr high where mr is the minimal radius of the hexagon=√3 r. The totalarea is approximately 62 r. In accordance with an embodiment, theCoverage Efficiency (CE) is defined as the Effective Area in units ofcoil radius (for circular coils) or length of side (for Hexagonal coils)divided by the number of Coils used. CE˜0.83 in this example.

To consider an example, one can take the maximum offset between thereceiver and charger or power supply coil to achieve sufficient outputpower to be half the width of a coil (assuming symmetrical coils). Usingcoils with different width or radii (in the case of circular coils) orother geometries would change this value. It can be shown that a hybridcoil with a PCB coil and a wound wire coil are placed on top of eachother is shown to have a more flat power transfer efficiency curve as afunction of offset between the charger or power supply and receiver coiloffsets. The general results and the operating principles for theembodiments discussed herein are valid regardless of what type of coil,geometry, or regulation is used to allow larger (or smaller)insensitivity to charger or power supply/receiver coil offset.

For the remaining portions of this document, embodiments are generallydescribed which use half the width of the charger or power supply coilas the maximum allowable offset between the charger or power supply andreceiver coil before the transferred power becomes lower than thedesired maximum transferred power value.

The sense and control mechanism in the Configuration shown in FIG. 36may be shared between a number of drive circuits to reduce parts countor may be integrated with each drive section. A number of other sensemechanism such as magnetic, optical, or capacitance sensors may also beused.

FIG. 37 shows an alternative embodiment in which the number of drive(and sensing) circuits may be reduced by using 1×N electrical orelectronic switches. In this embodiment, a number (N) of coils areconnected to a 1×N switch that is on the other side connected to a coildrive and sense circuitry. The switch periodically switches each of thecoils in rotation to the coil drive and sense circuitry. Once anappropriate receiver coil in the vicinity of a charger or power supplycoil is detected, that coil may be interrogated further to verify achargeable device is nearby and then charging or powering of the devicebegins.

One drawback of this scheme is that since each drive electronics modulecan at most only be connected to 1 coil out of N coils in each segment,2 devices placed on 2 different coils in that segment may not be poweredor charged simultaneously. In practice, since each device to be chargedwill cover a certain amount of area on the surface, by appropriatelysegmenting the pad and choosing the size of charger or power supply andreceiver coils, one can minimize the impact of this effect.

For an extreme case that N=NC (i.e. the number of coils in the pad), onecan use a single drive and sense electronics module to monitor and powerany coil in the pad thus greatly simplifying the architecture andpotentially the cost of the charger or power supply. However, only onereceiver coil, and hence only one device may be powered up or charged atany given time. The desirable characteristics of the 1×N switch are:

-   -   Low ON resistance: This would reduce wasted power in the form of        heat at the switch.    -   High current capability: For power charging applications,        depending on application and device to be charged, 0.5 A and        higher, up to several Amps of current may be carried in ON        state.    -   High reliability: Failure of a switch would render the related        segment dysfunctional.        Fortunately, the switching speed of the 1×N switch is not        critical for this application. For example, if it is desired for        the pad to have a 1 second response time (time it takes for the        pad to sense a device and begin charging), the switch must be        able to disconnect and establish a new connection in under 1/N        seconds (ignoring the time it takes for the sense and control        circuitry to work which can be extremely fast). As an example,        for N=10, this switch disconnect and connect time is under 100        msec, which is quite achievable. Even lower switching speeds are        acceptable for longer response times.

In accordance with an embodiment, the 1×N switches may be implemented byelectronics circuits or SPDT or DPDT IC switches, relays, MOSFETs, orMicro-Electro-Mechanical Systems (MEMS) switches. Other methods forswitching may also be employed.

As an example of a an IC switch for this application, a series of SinglePole Double Throw (SPDT) switches with relatively low R_(ds) of 80 mΩthat can be used in this application. An example of the SPDT isavailable in a Quad (four switches) pack and is capable of carrying 500mA which is sufficient for most low power applications. If largercurrent carrying capability is desired, two or more of the switches maybe used in parallel. This particular IC also incorporates over current,short circuit, and temperature sense circuitry which provides additionalsafety features for a system. A 1×N switch can be created by connectingseveral of such switches.

In accordance with one embodiment, the surface of a charging pad isdivided into segments where within each segment, a significant EffectiveArea wherein the center of a receiving coil can be placed to receivepower is created.

FIG. 38 shows a case where a three-coil layer PCB is arranged to providea cluster for uniform power in an area using only one coil powered atany given time. In this case, layer 1 comprises six coils arrangedaround a central coil for a total of seven coils. The second and thirdlayers comprise six coils total. In total, nineteen coils exist in thethree layers of the PCB.

FIG. 39 shows the coils are arranged such that by powering only one ofthe coils in the cluster, any receiver coil (for the receiver) placedwith a center within any location in the effective area receive thespecified power if the appropriate charger or power supply coil isactivated. When the three layers are stacked together, seen from above,the structure is as shown in FIG. 39. As described above, any pointwithin the Effective Area shown has the property that a receiver coilplaced with its center within this area is always within half a width ofthe center of at least one charger or power supply coil. Therefore, itcan receive the necessary minimum power or more with only oneappropriate charger or power supply coil activated.

For the case shown in FIG. 38 with nineteen distinct coils, five of thequad SPDT chips mentioned above can provide the necessary Switchingcapability to allow a single drive and sense circuit to sense thepresence or absence of a receiver coil near each coil. In accordancewith an embodiment, the sequence can be:

-   -   The switches are set so that the coil 1 in Layer 1 shown as        (1,1) in FIG. 38 is connected to a switching and sense circuitry        similar to the left side of FIG. 34 (i.e. the charger or power        supply in FIG. 34).    -   MCU1 gives a command to the FET driver to begin switching the        coil. The duty cycle may be set very low to generate a low        voltage in any potential nearby receiver coil.    -   If a receiver coil is nearby, it begins drawing power from the        charger or power supply coil. This can be sensed as a higher        than normal current draw in the current sense circuit of the        charger or power supply.    -   Additionally, the charger or power supply and receiver coil can        exchange a code to confirm that a valid device or battery with        appropriate circuitry is nearby and verified.    -   At this point, the amount of current through the sense circuit        is digitized by MCU1 and saved in its memory.    -   Alternately, the receiver circuit can note the amount of voltage        or power being received and report back to the charger or power        supply. This information can be encoded by modulating the input        impedance of the receiver circuit by MCU2. This information is        then sensed by the charger or power supply sense circuitry,        digitized by MCU1 and saved.    -   The FET driver and therefore the FET are disabled.    -   The switches are configured to connect the drive and sense        circuitry to the next coil (Coil (1,2) in this example).    -   Commands 2 through 8 are executed until all coils have been        activated and tested.    -   MCU1 compares the values received for sense currents and        determines which coil has the highest sense current when turned        on. This is the closest charger or power supply coil to the        receiver coil. If additional circuitry for confirmation of valid        receiver through exchange of code is implemented, the closest        coil has to also pass this test.    -   The appropriate coil is turned on and charging starts. An        additional verification can be performed prior to start of        charge.    -   The charging continues in open or closed loop depending on the        system architecture until end of charge is achieved. This is        either indicated to the charger or power supply by the MCU2 or        sensed in the charger or power supply sense circuit by a change        in the amount of current being drawn.

Depending on the characteristics desired and cost/performance tradeoffs,it may be decided that for each cluster, 2 or more drive and sensecircuits and a smaller number of switches are used.

FIG. 40 shows one configuration wherein the number of switches requiredis reduced to three to switch to any of the 20 coils in FIG. 39. Thefirst switch connects the Vc to one of the ports (outside or insidecontact point of the spiral coil) on every coil in one of the threelayers. The other ports of groups of three of coils from differentlayers are connected together and input into the switches 2 & 3 as shownin the figure. The outputs of Switch 2 & 3 are connected together, andconnect to the FET for switching. The center coil (1,7) is connected tothe poles of the switches by itself. This coil is often the most likelycoil for the receiver coil to be adjacent to since it is central.Comparing FIG. 40 with FIG. 34 shows that using this scheme, any one ofthe coils in the system can be connected by the switches to be driven bythe FET.

Depending on cost/performance trade-offs involved, it may beadvantageous to cut the number of switches by schemes such as shown inFIG. 40. Such a scheme can also be used to cut down the number ofswitches in a larger array. For example, the array in FIG. 36 comprising75 coils would require 19 Quad SPDT ICs to implement. However, by usingone Switch to choose one of the 3 layers and 7 switches to choose one ofthe 25 coils in each layer, one can achieve the same results with 8total switches.

With further cascading of switching layers, it is possible to furtherreduce this number. However, it must be noted that cascading ofswitching layers increases the Series Resistance along the current pathof the charger or power supply coil which is undesirable.

In the examples given above, the switching is shown for Point A in FIG.34 prior to the coils. However, Point B can also be used for thispurpose.

The associated electronics are shown on the perimeter of the coils butcan be placed in other locations too.

FIG. 41 shows a multi-charger or power supply pad that incorporates fourof the clusters shown in FIG. 39. A device to be charged or poweredwould have to be placed such that the center of the receiver coil iswithin one of the effective areas in one of the clusters or segments. Asan example, if the cluster is made of hexagons with side lengths r, ahexagonal Effective Area in the center of the cluster with a maximaldiameter of 5 r is created. The Effective Area˜19 r achieved with 19coils giving a Coverage Efficiency=Effective Area(in coil radius or sidelength Units)/Number of Coils=1.

For a typical coil of r=0.625″ side, this leads to a maximal diameter of3.125″. Such an almost circular Effective Area with a diameter of over3″ can be marked on the surface of the charger or power supply pad andallows the user to easily place the receiver coil inside (or on) amobile device such as camera, mobile phone, batteries, game players,etc. in the right location for charging without much alignment andeffort. Each of the clusters in the configuration shown in FIG. 41 canhave their own coil drive and sense circuits or may share this circuitrythrough multiplexing with switches.

In this way, a practical system for providing a large Effective Area ineach charging area (i.e. segment) while maintaining high power transferefficiency is developed. A significant advantage is also thatsimultaneous charging of multiple devices can be achieved.

It should be noted that the charger or power supply coils can bedesigned to be larger than the receiver coils. By doing so, one canobtain an even larger effective area and insensitivity to placement ofthe receiver coil. The Effective Area has a maximal diameter of 3 r.Other combination of coil patterns to achieve local positionindependence with a number of coils can be constructed.

FIG. 42 shows a cluster of 2 layers of 3 coils and a central coil (total7 coils) that can create an effective area of 3 r. In practice, such anarea may be sufficient for many applications. It will be noted thatwhile Hexagonal coils are shown in many of these figures, a combinationof Hexagons and/or circles, or other shapes can be combined to providethe best efficiency/position independence performance. Similarly, thesize and shape of the receiver can be non-Hexagonal.

For example, in FIG. 42, the central and the receiver coil can insteadbe circular (spiral coil) and the central charger or power supply coilis the most likely charger or power supply coil for the receiver coil tobe on top of. If the receiver coil is placed on any other position, ahexagonal coil is the closest coil and be powered. In accordance withother embodiments, the central coil in FIG. 16 can be larger than thereceiver coil and cover most of the likely central area. The remainderof the coils would only be used if the receiver is placed in extremeoutside locations.

It must be noted that the foregoing description describes the situationwherein the transmitted power drops to acceptable levels when the coilcenters are offset by half the radius. In practice, this value can bedifferent and by using a combination of coil patterns and sizes andregulation of the transmitted power, uniform power transmission acrossan area can be maintained.

While the use of IC switching elements has been discussed above, otherswitching mechanisms such as MEMS, relays, etc. can be used to achievethe results. In accordance with other embodiments, the switching may beimplemented by creating a deformable layer under the coil layers to actas the switch. Each spiral coil discussed here has 2 ports with one atthe outside diameter wherein the coil starts and one at the centerwherein the coil terminates.

FIG. 43 shows a mosaic of hexagonal coils with the central port to eachcoil shown as circles. In accordance with an embodiment, one of theports of all of the coils in the 3 layers (in this case, the outsideport) is connected to a common point, called here P1. The other port ofeach coil (shown as the central one here) in the mosaic pattern of FIG.42 is brought down through vias to a common layer at the bottom of themulti-layer PCB and connected to a copper pad with a certain surfacearea. Such a pattern seen from above (the same side as FIG. 43) is shownin FIG. 44.

FIG. 44 shows the top view seen from the same side. The side view of thepad has integrated MEMS switch for contacting individual coil contactpads.

In an earlier U.S. patent application Ser. No. 11/669,113, the use ofattracting magnets placed at the centers of an inductive charger orpower supply's PCB coil and the center of the receive coil to align andcenter the 2 parts conveniently has been described. Such techniques wereused in the charger or power supply for mobile device or batteryalignment.

In accordance with a present embodiment, a planar conductive layer orconductive traces patterned with conductive pads similar to the coilport pattern shown in Top part of FIG. 44 and all connected to a commonpoint (called P2 here) is created on a flexible material film. Examplesof the material for the flexible film are mylar, polyimide, flexible PCBmaterial such as Kapton, etc. or plastic. At the center of each of thepads, a small magnet or ferromagnetic material is attached to the otherside of the film. Alternatively, a layer of ferromagnetic material isdeposited and patterned to have a pattern similar to FIG. 45 top so thatonly material with a pattern similar to the PCB port pad remains. Theflexible film is attached to the bottom of the PCB such that a small gapbetween the top layer of the film and the bottom of the PCB is createdby a spacer. The side view of the MEMS charger or power supply pad isshown in FIG. 44.

The entire package shown in the bottom of FIG. 44 has 2 electricalconnection points. One from the PCB, called P1 that is connected to oneof the ports of all of the coils in the 3 layers of the PCB (in thiscase the edge port). The other connection is to the common pads on theflexible film. This is called P2. Looking at FIG. 34, the entire packagecan be treated as L1, and connect P1 to point A in this circuit and P2to point C.

Ordinarily, none of the coil center ports are connected to the contactpads on the flexible film and therefore the circuit is not completed. Ifa receiver coil with a magnet attached to the back of its PCB coil andthe magnet oriented with correct polarity is brought close to the pad,it attracts the magnet or patterned ferromagnetic layer at the center ofthe nearest charger or power supply coil and at the bottom of theflexible film towards itself. This causes the top conductive layer onthe flexible film to make contact with the center port of theappropriate coil and close the circuit. In this way, current can flowonly through the appropriate coil and then activate it.

In accordance with an embodiment, to avoid oxidation of the contact padsat the bottom of the PCB and the flexible film contacts, these surfacescan be protected by deposition of additional layers such as gold orother material on top of the copper. Such processes are often used inPCB manufacture to protect exposed contacts. In addition, the PCB padpackage can be hermetically sealed to avoid dust contamination on thecontacts. Additionally, the volume inside can be filled with an inertgas such as nitrogen.

By optimizing the surface area of the contact pad and the flexible filmcontact areas and material composition, low contact resistance can beobtained. Other parameters to optimize are the area of the magnet ormagnetic material and the type of material used.

The configuration above is provided by way of example. In accordancewith other embodiments, it is possible to connect the components in adifferent manner, or to place in an external drive circuit in adifferent configuration to achieve the desired result. A 3 layer boardhas also been used to demonstrate this approach. Simpler constructionswith 1 or 2 layers or configurations wherein the coils in the differentlayers have different functions or sizes and provide different powerlevels can also be implemented. The advantages of this approach are:

-   1—High efficiency: Only the appropriate coil for high coil overlap    is activated.-   2—Position Independence: The receiver coil can be placed anywhere    with its center in the Effective Area and achieve specified power    transfer.-   3—Low cost: The pad does not use any IC switching elements for    connecting to the appropriate coil.    As described above, in accordance with an embodiment the entire    package in FIG. 44 is connected between points A and C in the    circuit of FIG. 34. One example of the operation of the system is    described in more detail here:    -   MCU1 gives a command to the FET driver periodically to begin        switching the coil. The duty cycle may be set very low to        generate a low voltage in any potential nearby receiver coil.    -   Ordinarily, none of the coils is connected to point C in        FIG. 34. Therefore, no current is sensed in the current sense        circuit.    -   If a receiver coil is placed on the pad, it will cause the        appropriate charger or power supply coil center port to contact        the pad on the flexible film and therefore the appropriate coil        is contacted to points A and C in FIG. 34.    -   The receiver coil begins drawing power from the charger or power        supply coil. This can be sensed as a higher than normal current        draw in the current sense circuit of the charger or power        supply.    -   Additionally, the charger or power supply and receiver coil can        exchange a code to confirm that a valid device or battery with        appropriate circuitry is nearby and verified.    -   Once MCU1 determines that an appropriate receiver coil is on the        pad and ready to draw power, the FET is turned on and charging        starts. An additional verification can be performed.    -   The charging continues in open or closed loop depending on the        system architecture until end of charge is achieved. This is        either indicated to the charger or power supply by the MCU2 or        sensed in the charger or power supply sense circuit by a change        in the amount of current being drawn.

The description provided above describes what happens when theactivation of the MEMS switch occurs through magnetic attraction. Inaccordance with some embodiments, the switch can be designed such thatit closes at the appropriate location due to static attraction,pressure, temperature change, or other mechanism.

In the MEMS system described above, a disk or other magnet in thereceiver coil attracts a magnet or patterned ferromagnetic layerattached or deposited under the flexible film to close the contactbeneath the appropriate charger or power supply coil to the FET.However, in other embodiments a ferromagnetic layer can also be used inthe middle of the receiver coil (on the front of the PCB, its back orseparate layer from the coil layer) and use either permanent magnets ordeposit or sputter, etc. a patterned ferromagnetic layer that ispermanently magnetized behind the flexible layer film. In this way, thecharger or power supply pad would contain multiple magnetic pointscorresponding to the centers of the coils. When a ferromagnetic materialis brought close to the pad, the appropriate coil is activated. To avoidfalse starts with metallic objects placed on the pad, secondaryverification techniques, as described above, can be used, including insome embodiments an exchange of code between the charger or power supplyand receiver coil.

Examples of metals that can be used are Ni, Fe, Co, or various commonlyused alloys. These can be deposited on a flexible film in a variety ofways such as sputtering, evaporation, e-beam, plating, etc.

The system shown in FIG. 44 is mostly designed to operate with a singleFET and allow charging of a single device somewhere on the pad. If 2devices are placed on the pad and 2 coils are connected to the pad, thepower transferred may not reach the full specified power and it may notbe clear which device is sending or receiving the control signals duringcharging.

In accordance with an embodiment, to overcome these issues, a segmentedpad where clusters of charger or power supply coils are attached toindividual drive and sense circuits and are independent of each othercan be used.

The X-Y area is divided into segments (in this case 4 shown). One coilin each section can be driven by an appropriate FET and sense Circuitfor that segment. Top: The pattern for contact pads at the bottom layerof the PCB. Each pad is connected to the central port of a coil in oneof the 3 layers above. The top view is shown here. Bottom: The side viewof the pad with integrated MEMS switch for contacting individual coilcontact pads. Spacers at the edges and the walls of the segment areaskeep the flexible film at a pre-determined distance from the bottomlayer of the PCB.

FIG. 45 shows the architecture of the segmented MEMS charger or powersupply pad in accordance with an embodiment. Each segment comprising anumber of coils is connected to points A and C of a different driver andsense circuit. Thus, devices placed inside each segment can be drivenwith their own driver and are independent. In this way, several (in thiscase 4) devices can be charged or powered simultaneously.

In FIG. 45, additional spacers are placed at the boundaries of thesegments. These spacers may help with keeping the flexible film/PCB gapconstant and operation of the flexible film uniform along the X and Ydirection. Such spacers interspersed in the X-Y plane between the PCBand flexible film layer may be used regardless of whether the pad issegmented electrically or not.

In accordance with some embodiments, the MEMS switching method describedhere can also be applied to the cluster geometry shown in FIG. 41 or anyother geometry.

Conductive Multi-Charger or Power Supply Surface

As discussed above, in accordance with some embodiments, another methodfor charging or powering multiple devices on a common charger or powersupply surface is to incorporate a number of connector points or stripsinto the pad. The user can place a device with an appropriate connectoron a pad or similar object and receive power through matching contactson the pad. FIG. 46 shows a general diagram for this approach is shownin. In this approach, one or more regulated power supplies are connectedto the charger or power supply pad. The pad comprises an array ofcontacts or strips of exposed connector.

FIG. 47 shows an array of contacts on the surface of a pad. In FIG. 47,each position comprises a Voltage and Ground contact. In this picture,the connector is shown as a recessed circle similar to a washer whereone contact is in the middle and the other contact is in the body oroutside of the circle. Other connector geometries are possible.

A device with an appropriate mating connector at its bottom or in aplug-in unit for after-market applications can be placed on the pad andthe connectors on the device make appropriate contacts to the padcontacts if placed on one of the contact points. In accordance with anembodiment, the connectors on the surface of the charger or power supplypad are connected to a number of switches which are connected toregulated power supplies and sense circuits as shown through switcharrays as shown in FIG. 46. MCU1 periodically turns ON one of theregulated power supplies. The switches are set such that a connection ismade to the 2 contacts of a contact point in the pad. The sense circuitdetects any possible flow of current. If a current flow is detected, thesystem may verify the presence of a valid receiver through exchange ofinformation through the contact with a MCU2 in the receiver. If nocurrent is being drawn or the verification process fails, the MCU1reconnects the supply to the next contact position. By rastering theentire pad periodically, contact to several devices on the pad forcharging or power can be established. A diode D1 can be used forprotection against reverse voltage, a Capacitor (C1) to filter anypotential noise on the regulated power supply output, and MCU2 to enablecommunication between the Charger or power supply and the Receiver areshown. The receiver may also incorporate a voltage regulator to providea constant voltage (or voltage in the acceptable range for operation) toMCU2. This voltage regulator just provides the low power necessary forthis, and is not in the path of the main power going into the battery.Any power loss due to this regulator is small because it is very lowpower and does not affect the overall system efficiency much. It ismainly used to keep the MCU active during startup or other changes sothe communication with charger or power supply is maintained. However,these components are optional and may not be present depending on thearchitecture used. The description provided herein does not depend onuse of these components for operation.

If the ground (through a sense circuit) contact for all positions isconnected together, then Switch Array 2 can be eliminated. Care must betaken to interpret the received signals in interpreting the currentsense values since it is the sum of currents from all devices beingcharged.

The switching arrangements discussed above for the Inductive cases canbe modified and used for this type of conductive switching as well. Inaddition, the MEMS based approach shown above are applicable to thisapplication.

An embodiment for a universal charging pad using conduction is shown inFIG. 48. In this case, one of the contact points for each position (e.g.Ground contact) is connected together throughout the pad and connectedto the appropriate location (Ground through the sense circuit in thiscase). The other contacts are brought through the charger or powersupply surface to the bottom of the surface and contact pads are formed.

Top: The pattern for contact pads at the layer below the connectors. Oneof the contact points for each position (e.g. Ground contact) isconnected together throughout the pad and connected to the appropriatelocation (through Sense circuit to Ground in this case). Bottom: Sideview of the pad with integrated MEMS switch for contacting individualcontacts to the power supply. Spacers at the edges keep the flexiblefilm at a pre-determined distance from the bottom layer of the PCB.

In accordance with an embodiment, a planar conductive layer orconductive traces patterned with conductive pads similar to the chargeror power supply surface contact pattern shown in Top part of FIG. 48 andall connected to a common point (called P2 here) is created on aflexible material film. Examples of the material for the flexible filmare mylar, polyimide, flexible PCB material such as Kapton, etc. orplastic. At the center of each of the pads, a small magnet orferromagnetic material is attached to the other side of the film.Alternatively, a layer of ferromagnetic material is deposited andpatterned to have a pattern similar to the Top in FIG. 47 so that itonly material with a pattern similar to the charger or power supplysurface pad pattern remains. The flexible film is attached to the bottomof the charger or power supply surface such that a small gap between thetop layer of the film and the bottom of the charger or power supplysurface is created by a spacer.

FIG. 48 shows the side view of the MEMS conductive charger or powersupply pad. Using the MEMS conductive charger or power supply padeliminates the need for switching arrays.

In accordance with an embodiment, the entire package shown in the bottomof FIG. 48 has two electrical connection points. One from the topsurface, called P1 that is connected to one of the connector points ofall of the connector positions on the charger or power supply surface(Ground in this case). The other connection is to the common pads on theflexible film. This is called P2, and is connected to the other positionin the circuit. For example, for the geometry discussed here, P1 can beconnected to Point B in FIGS. 49 and P2 connected to Point A. FIG. 49 isa generalized block diagram of a charger or power supply pad withmultiple regulated power supplies.

The case discussed here and the pad in FIG. 48 enable connection of oneregulated supply to one or more devices placed on the pad. However inthe case of multiple devices on the pad, the voltage characteristics ofthe device would have to be identical to the first one and the sum ofpowers being drawn from the supply not exceed the maximum rating of thepower supply. A more generalized approach wherein differentvoltages/power can be supplied to different devices is discussed infurther detail below.

Ordinarily, none of the connectors are connected to the contact pads onthe flexible film and therefore the circuit is not completed. Inaccordance with an embodiment, if a receiver with a magnet attached tothe back or perimeter of the connector and the magnet oriented withcorrect polarity is brought close to the charging surface, it attractsthe magnet or patterned ferromagnetic layer at the center of the nearestcontact pad and at the bottom of the flexible film towards itself. Thiscauses the top conductive layer on the flexible film to make contactwith the contact pad for the appropriate connector at the bottom of thecharger or power supply surface and close the circuit. In this way,current can flow only through the appropriate connector into thereceiver circuit and the device to be charged.

As described above, to avoid oxidation of the contact pads at the bottomof the charger or power supply surface and the flexible film contacts,these surfaces can be protected by deposition of additional layers suchas gold on top of the Copper. Such processes are common to protectexposed contacts. In addition, the pad package can be hermeticallysealed to avoid dust contamination on the contacts. Additionally, thevolume inside can be filled with an inert gas such as nitrogen.

By optimizing the surface area of the contact pad and the flexible filmcontact areas and material composition, low contact resistance can beobtained. Other parameters to optimize are the area of the magnet ormagnetic material and the type of material used.

Top: The pattern for contact pads at the layer below the connectors. Oneof the contact points for each position (e.g. Ground contact) isconnected together throughout the pad to form contact point P1. Bottom:Side view of the pad with integrated MEMS switch for contactingindividual contacts to the power supply. Spacers at the edges and thewalls of the segment areas keep the flexible film at a pre-determineddistance from the bottom layer of the PCB. The contact pads in eachsegment of the flexible film are connected together to form contact P2for each segment.

FIG. 49 shows another embodiment where several regulated power suppliesprovide power to the pad. This allows charging of several devicessimultaneously.

FIG. 50 shows an alternative embodiment using a segmented surface. Theoperation of this is similar to previously described except that the topand bottom contact points for each segment P1 and P2 are connected tothe appropriate positions in B and A in FIG. 49 so that each regulatedpower supply is connected to one of the segments in the charger or powersupply surface when the circuit is closed. In this way, a device placedon each of the segments can be powered by the regulated power supply atits required voltage and power level.

Electromagnetic Shielding

Electromagnetic Interference (EMI) is an important aspect of performanceof any electronic device. Any device to be sold commercially requiresadherence to regulation in different countries or regions in terms ofradiated power from it.

For an inductive charger or power supply comprising a number of coilsand electronics switches and control circuitry, the main sources ofnoise include:

-   -   Any potential radiated noise from switching FETS, drivers, etc.        or sense and control circuitry. This noise can be at higher        frequency than the fundamental drive frequency of the coils and        can be emitted away from the charger or power supply because of        the frequency. This noise can be minimized by optimizing the        drive circuit to avoid sharp edges in the drive waveform and        associated noise.    -   Noise from copper traces with ac signals. This noise can also be        at higher frequency and emit away from the charger or power        supply. The length of these paths must be minimized.    -   EM emission from the switched coil. For coils described here and        driven in the 100's of kHz up to several MHz, the wavelength of        the Electromagnetic (EM) field generated can be in the hundreds        of meters. Given the small length of the coils windings (often 1        m or less), the coils used are not efficient far-field        transmitters of the EM field and the generated EM field is in        general highly contained near the coil surface. The magnetic        flux pattern from a PCB coil is highly contained in the area of        a coil and does not emit efficiently away from the coil.

Care must be taken when designing the current paths, and in someembodiments shielding of the FETs or other ICs or electronics componentsmay be necessary. In addition, switching the coils with waveforms thathave higher frequency components, gives rise to noise at higherfrequencies. In any of the above geometries described, incorporation ofconductive layers and/or ferromagnetic layers in the system can shieldthe outside environment from any potential radiative fields. Theconductive layers may be incorporated in the PCB to eliminate the needfor additional separate shielding layers.

In the examples provided above, while the 3 coil layers can beincorporated into PCB layers, the electronics components can be placedon the lower most surface of the PCB to allow a flat surface on the topand allow receiver coils to get as close as possible to the charger orpower supply coils. One possible arrangement for the location of theelectronics components at the bottom surface of the total PCB stack isshown. In this case, in some or all of the layers above, the PCB layerscan incorporate Copper sections in the areas shown in black in thisfigure. By appropriately grounding these sections and providingadditional conductive and/or magnetic layers below the electronicscomponents, the EMI can be significantly reduced.

In accordance with an embodiment, another method for minimizing theeffect of the copper traces in the PCB is to sandwich them betweenlayers of conductors in the PCB. In a multi-layer PCB, the coppertrances and connections to all the components and coils can be forexample, be in a middle layer and the necessary connections to the ICsor other layers be made through vias. Given that the magnetic flux ishighly contained within the coil area, the layer containing the coil oranother layer below or above can contain a substantially continuouslayer of copper covering everything except the area of the fluxgenerated by the PCB (very close to the outside ring of the coil). Byhaving two or more conductive PCB layers for shielding sandwiching thesignal and current paths, most of the noise generated can be shieldedvery close to the source. Since the noise from the PCB is minimal anddoes not radiate, the remaining source of noise, the electronics, FETS,etc. can be shielded by covering the section with these devices with ametallic cover or shield.

Similar types of judicious incorporation of grounded Copper layers inthe PCB layers in any of the designs above can significantly reduce anypotential EMI issues without requiring additional shielding layers.

FIG. 51 shows a standard used within the European Union for measuringemissions from a product. In this case, the emissions from a product aremeasured at 10 m distance. This test (EN 55022) looks for emissions from30 MHz to 1 GHz. Limits for Class A and Class B certification are shownin the Figure.

FIG. 51 shows a typical scan of emissions from an inductivemulti-charger or power supply pad. As discussed above, the radiation atthe fundamental operating frequency (100's of kHz to several MHz), canbe self-contained within the coil area. However, noise at higherfrequencies (such as the test range of 30 MHz to 1 GHz) must be reducedto avoid interference with other nearby electronic devices.

Metallic and/or Ferromagnetic layers are often included in electronicdevices to reduce their EM emission. An example of such layers isdescribed in U.S. Pat. Nos. 6,888,438, and 6,501,364. In theseinstances, PCB coils are formed on two sides of a PCB, and ferromagneticand copper layers are placed on each side of the PCB to limit emissionsfrom a package containing such a transformer.

Frequency Selective Electromagnetic Shielding

In accordance with some embodiments of the inductive universal chargeror power supply pad described herein, the inclusion of metallic and/orFerromagnetic layers at areas that are potential sources of emissionsuch as FETs, etc. may be beneficial. However, a method that wouldwholly cover the charger or power supply pad package to eliminatepotential for escaping EM fields may provide benefits.

Given that the inductive charger or power supply pad operates bygenerating an oscillating magnetic field, such an approach does not seemfeasible as it would block such a field from being sensed by thereceiver coil.

In accordance with an embodiment, a method is described herein thatallows the inductive pad to emit EM waves efficiently for operationwhile simultaneously providing shielding to high frequency EM fields.Such operation is achieved by taking advantage of the skin effect inconductors.

The skin effect is the tendency of an alternating electric current (AC)to distribute itself within a conductor so that the current density nearthe surface of the conductor is greater than inside the material. Thatis, the electric current tends to flow at the “skin” of the conductor.

The skin effect causes the effective resistance of a conductor toincrease with the frequency of the current and has practicalconsequences in the design of radio-frequency and microwave circuits.

The current density J in an infinitely thick plane conductor decreasesexponentially with depth δ from the surface, as shown below:J=J _(S) e ^(−δ/d)where d is a constant called the “skin depth”. This is defined as thedepth below the surface of the conductor at which the current densitydecays to 1/e (about 0.37) of the current density at the surface. It isgiven by:

$d = \sqrt{\frac{2\;\rho}{\omega\;\mu}}$Where:

-   -   ρ=resistivity of conductor    -   ω=angular frequency of current=2π×frequency    -   μ=absolute magnetic permeability of conductor=μ₀·μ_(r), where μ₀        is the permeability of free space and μ_(r) is the relative        permeability of the conductor.        It is important to note that d decreases rapidly with frequency.        The magnetic and electric field similarly get attenuated        traveling through a sheet of a conductor. Using the values for        conductivity of copper (5.8×10⁷ Siemens/m), the absorption going        through a single layer of copper with various thickness can be        calculated.

FIG. 52 shows the absorption through a copper layer of 70 μm and 7 μm.While the 70 μm layer provides very high attenuation in the region ofinterest (30 MHz to 1 GHz), the attenuation is excessive in most casesand is only needed in extraordinarily noisy circumstances.

As described herein, the transmitted power is considered through a verythin conductive layer.

FIG. 53 shows how the attenuation values are shown for Copper andAluminum (conductivity of 3.76×10⁷ for 99.99% Al) layers for severalthicknesses.

For these calculations, the placement of the layer with respect to thesource of the EM field needs to be included. In these calculations, thesource is assumed to be 0.5 mm under the layer. This is similar toplacing the layer essentially directly on the source of the field.

It will be noted that, for very thin layers of Copper and Aluminum, downto 1 micron thickness, very high attenuation values at frequencies over1 MHz are obtained. The attenuation of 1 μm layers of Copper andAluminum at 10⁹ Hz are respectively 32 dB and 28 dB and are comparable.However, at 1 MHz or below, the attenuation in either material for sucha thin layer is minimal. In accordance with some embodiments, thisbehavior or characteristic can be exploited.

FIG. 54 shows Transmitted EM Power through Copper and Aluminum layers ofvarying thickness for an incident EM field at 1 MHz which is a typicaloperating frequency for the type of inductive universal charger or powersupply described herein. Below 5 μm thickness, the transmitted powerexceeds 95%. Aluminum in particular (due to its lower conductivity), hasa wide range of thicknesses that allows a 1 MHz radiation to transmitthrough without much attenuation.

As discussed above, in some embodiments of the inductive charger orpower supply device described herein, the generated EM field at theoperating frequency of the charger or power supply (typically ˜1 MHz),is generated by an inefficient PCB coil antenna and is mostly confinedto the area immediately near the coil (to be picked up by the receivercoil). However, any noise generated by driving the coil at thisfundamental frequency (due to nonlinearities at the components,non-sinusoidal signal, or at the FET or the FET driver) or any noisegenerated at any other location in the charger or power supply devicecurrent paths or components or the receiver (including noise generatedat the receiver rectifier), can have components that are much higher infrequency. It is desirable to suppress such noise to the extentpossible.

In accordance with an embodiment, a very thin layer of a conductor (suchas Copper or Al, organic conductors, nanotech materials, nanotubes, orother material), covering all or part of the charger or power supplyand/or receiver circuit can be used to allow the desired low frequencycomponents (Several MHz or below) to travel through without attenuationwhile severely reducing the higher frequency noise. In accordance withsome embodiments, the entire inside or outside surface of the charger orpower supply and/or receiver package circuitry or part of it is coveredto achieve this frequency selective shielding without dramaticallyaffecting the fundamental operation of the device.

In one embodiment, the entire inside or outside of the package for theinductive charger or power supply and/or the receiver for such a chargeror power supply is covered by a thin layer of a conductor (15 μm thickor less or preferably less than 5 μm thick). The conductor can bemetallic as discussed above, metal alloys, organic, nanotech materials,nanotubes, etc. At high frequencies, such a layer reduces the emitted EMpower considerably (greater than 20 dB or even 30 dB) while allowingmost (>90%) of the fundamental operating frequency power to transmitthrough the layer. The conductive layer can be directly deposited on theparts. To avoid shorting of any electronics or connectors, contacts, adielectric layer, paint or other material must be first deposited.Alternatively, the conductive parts can be masked off so as not tocontact the EM shielding conductive layer.

The deposition of the conductive material can be done in a variety ofmanners (sputtering, evaporation, electroplating, coating throughdipping, Langmuir Blodgett, painting, etc.) for different materials.Recently, an inexpensive method (Ecoplate) for conformally coating anymaterial with metallic or metal alloy layers at room temperature hasbeen developed. In this process, a spray of molten metal at controlledtemperature and velocity instantaneously cools on incidence with asubstrate and forms a conformal layer covering the entire or part of apart. The EM conductive shield can also be deposited onto a substratesuch as a polymer (e.g. mylar, polyimide, polyurethane, plastics, etc.),rubber, etc. and the conductive layer coated polymer be applied to theinside or outside of the part. Anti-static bags are an example of ametalized polymer material. Aluminum is commonly used for thisapplication.

In another embodiment, the PCB boards, electronics components, and thecoils in the charger or power supply and/or the receiver are covered bya nonconductive layer (such as a dielectric, paint, etc.) and thencovered completely or locally by a conductive layer of appropriatethickness either directly deposited on the board and the electronics orindirectly with a polymer or similar backing (as described above).

The optimum thickness of the conductive material is highly dependent onits conductivity. By choosing the material composition and thickness,one can obtain the desired combination of EM noise suppression andtransmission of fundamental frequency.

It is also possible to combine conductive layer materials andthicknesses to construct a more tailored frequency response. Such anapproach is commonly taken in the optical domain to fabricate wavelengthdependent filters.

In those embodiments wherein the conductive layer covers the charger orpower supply and/or receiver coil, it may be desirable to generate an EMfield with a charger or power supply coil and then, after passing theemitted field through such a conductive layer, turn it back to DC powerthrough the receiver coil and rectification. Since the conductive layeris a frequency dependent filter, in this process, this removes or weakenany higher frequency signals and enables the receiver to receive acleaner, and depending on the design, more sinusoidal signal. Such highfrequency noise is often related to not-only EMI disturbance and lack ofsignal to noise ratio in the electronic device to be charged. Inaddition, the higher frequency noise causes non-optimum operation of thereceiver and possibly heating of the receiver or other components. Byremoving the generated noise, electrical and thermal/environmentalperformance of the charger or power supply and receiver system may beimproved.

Such a physical filtering of an electrical system is analogous to anoptical signal being filtered in the wavelength domain (by an opticalfilter, grating, etc.) before reaching a receiver. The SNR andefficiency of the system is improved in this way.

Use of Magnets for Alignment of the Coils

FIG. 55 shows a method for obtaining local alignment independencebetween the coils in the charger or power supply and the receiver areshown therein. In accordance with an embodiment, by using small magnetsbehind (on the side opposite to the side facing the surface of thecharger or power supply) the center of each coil in the charger or powersupply, and behind (on the side opposite to the side facing the surfaceof the charger or power supply) the coil in the receiver, such that themagnets attract each other, a charger or power supply system can beprovided wherein the user can easily find the location where the chargeror power supply coil is located, without providing any physical featuresand/or marking on the surface of the charger or power supply. This maybe advantageous in enabling charger or power supplies which can be usedwith any device to be charged without need for special alignment or sizefeatures. This allows charging of any size and shape device and/orbattery. In this geometry, shown in FIG. 55, the magnets can be thinflat or other shape magnets placed at the center of the coil and allowthe device or battery to be charged to be rotated around the charger orpower supply coil with no effect.

As described above, by enabling the coil in the charger or power supplyto move laterally (and somewhat vertically) in the plane of the chargeror power supply surface, automatic alignment of the charger or powersupply and device and/or battery coil can be achieved when a deviceand/or battery is laterally brought close to the center of the chargeror power supply coil.

If magnets used for this application are electrically conductive, thensome of the field generated by the coil will generate currents in themagnet and heat the magnet, decreasing the efficiency of the system andgenerating unwanted heat. This effect especially becomes important asthe field strength of the coil is increased for higher powers.

In accordance with some embodiments, methods for dealing with thisproblem can be included, such as:

-   -   Since the currents are created by eddy currents generated in the        magnets, use of non-conductive and/or low conductivity magnetic        material can improve this condition.    -   The magnet can be constructed of thin flat magnet material with        laminate in between the layers to decrease the current flow and        loss of power.

FIG. 56 show an embodiment in which the magnets can be broken or dividedinto sections, such as semi-circles with a gap or non-conductivematerial in-between to avoid current circulation. By having each set ofmagnets behind a coil to be made of two or more sections, the electronsare disrupted from circulating and generating strong eddy currentsleading to heating and power loss. In this figure, each set of magnetsbehind a coil are made of semi-circular magnets. The poles of the magnetare aligned with the South or North pole facing the surface of thecharger or power supply. The magnet in the device or battery have theopposite polarity so that the magnets of the charger or power supply andthe device and/or battery attract. By having each set of magnets behinda coil to be made of two or more sections, the electrons are disruptedfrom circulating and generating strong eddy currents leading to heatingand power loss. In FIG. 56, each set of magnets behind a coil are madeof two semi-circular magnets.

FIG. 57 shows an embodiment in which one or more alignment magnets canbe used behind each coil. However, in accordance with an embodiment themagnets are placed such that each magnet does not cover an areaextending beyond the center of the coil. In other words, the surface ofthe magnet does not cover the center of the coil and thereby does notallow circular currents to be set up in the magnet as effectively. Inthis way, the eddy currents set up are much weaker and much smallerpower dissipation in the magnets occurs. Alignment magnets at center ofcharger or power supply and device and/or battery coils for alignment ofthe two coils are attached to the back of the coils in such a way thatthe area of the magnet does not extend beyond the center of the coil. Inthis way, the eddy currents created are much weaker and much less poweris lost to the magnets. In this figure, two magnets are shown per backof each coil (four total for a pair of charger or power supply andreceiver magnets). However, any number of magnets from one to many canbe used.

Additional Applications—Charger/Power Supply with Self-Powered Operation

FIG. 58 shows an illustration of a device for inductive power chargingthat includes an internal battery for self-powered operation, inaccordance with an embodiment. As shown in FIG. 58, an inductivecharging unit such as an inductive pad 360 includes a rechargeablebattery 364. The unit is normally operated with, or is occasionallycoupled to, power input from an electrical outlet, or from a dc sourcesuch as a standard automobile 12 volt dc outlet, or from an outlet in anairplane or an external dc source, or from another power source such asthe USB outlet from a computer or other device. Alternatively, the powercan come from a mechanical source such as a windmill, or a human-poweredcrank handle. The unit can include coils 362 that are energized totransfer power to receiver coils in mobile electronics devices such asmobile phones, MP3 players, radios, cd players, PDAs, and notebookcomputers. At the same time, the input power charges the rechargeablebattery inside the unit itself. When the external power source to theunit is disconnected, or when no input power is provided, the unitautomatically switches its operation from its charged internal battery.Alternatively, the unit's operation can be switch-operated by user. Inthis way, users can continue to charge their devices by placement on theunit without any outside power source. This use can continue until theexternal power is restored or until the internal battery is completelydischarged.

The ability of the unit to continue charging depends on the capacity ofthe battery included. Thus, for example, with a 1500 mAH internalbattery, the unit is able to charge a mobile phone with a 1000 mAHbattery completely if the losses due to conversion efficiency, operationof the circuitry in the unit, and other losses are up to 500 mAH.

In other embodiments of an embodiment, the unit can be powered by otherpower sources such as a fuel cell that generates power from methanol orother sources. The unit can also be connected to the electric gridthrough an outlet or to an external DC power source such as power froman outlet in a car or airplane or be itself charged or poweredinductively by another unit. However, when not connected to outsidepower, the unit can be powered by its internal power generator from thefuel cell and can charge devices placed on it inductively.

FIG. 59 shows an illustration of an alternate embodiment of an inductivecharger or power supply unit or pad 370 with a solar cell power sourcefor self powered operation, in accordance with an embodiment. As shownin FIG. 20, the surface of the unit can be covered by a solar panel orsolar cell 376. In normal operation, the unit can be powered-up orcharged by connection to an electric outlet or external DC source. Butwithout external electric power, the panel generates electric power thatis used to power the charger or power supply which in turn can chargedevices placed on it through the inductors in the unit. In someembodiments the unit can also include a rechargeable battery 374 thatcan be charged when the unit is either connected to external electricpower or charged by the solar cells on the surface of the unit. Thisbattery can then operate the unit when the unit is either not connectedto external electric power or the solar cell is not generating enoughpower to run the unit such as during operation at night.

FIG. 60 shows an illustration of an inductive charger or power supplyunit with an incorporated communications and/or storage unit, inaccordance with an embodiment. As shown in FIG. 21, in accordance withsome embodiments the charger or power supply, including for example theregular charger or power supply 380, and the solar-cell powered chargeror power supply 382, can further comprise an optional communicationsand/or storage unit, for storage of data and transmission of data to andfrom a mobile device being charged. Examples of components that can beincorporated include Bluetooth, Near-field Communications (NFC), WiFi,WiMax, wireless USB, and proprietary communications capabilities,including means of connecting to the Internet.

Additional Applications—Inductive Charger Applications and Kiosk

The technology described herein may also be used for other applications.In some applications, it may be desirable to build the inductive (asdescribed above) or wire free charger or power supply into a case for anelectronic device, a briefcase, or other carrier such as a box, holder,or container in a car or other wise. An example can be a brief case,hand bag, or back pack where the bottom part or the outside surface hasan integrated charger or power supply. Any device enabled to receivepower from such a charger or power supply (device containing coils andthe appropriate electronics to receive power or with appropriatecontacts for wire free charging) can be placed on or inside such abriefcase and be charged. The charging circuitry can be powered byplugging the briefcase, handbag, or back pack into an outlet power orhaving internal batteries that can be charged through power from a wallplug or by themselves being inductively charged when the briefcase,handbag, or backpack is placed on an another inductive or wire freecharger or power supply. Uses can be applied to any bag, container, orobject that can be used to essentially charge or power another device.This first object can itself be charged or powered through an outletdirectly by wires or wirelessly through an inductive or wire freecharging system. As an alternative, the first object (the charger orpower supply) can be powered by solar cells, Fuel cells, mechanicalmethods (hand cranks, pendulums, etc.).

In all of the above case, it is possible for the functions of theinductor or wire free charger or power supply and the power source forthe charger or power supply (battery, fuel cell, solar cell, etc.) to beseparated. Furthermore, in some cases, the charger or power supply partcan be separated from a portable power source to operate it (such as arechargeable battery) which is in turn powered or charged by anothersource (power outlet, fuel cell, solar cell, mechanical source, etc.).The three parts can be in the same enclosure or area or separate fromeach other.

An additional example may be an after market inductive or wire freecharger or power supply for a car where the inductive or wire freecharger or power supply or pad including a solar cell on the pad or inanother area and connected to the pad by wires is used to charge mobiledevices. Such a device placed on the dashboard or tray between seats ora special compartment can be used to charge a number of devices such asphones, MP3 players, cameras, etc. Devices such as GPS navigationsystems, radar detectors, etc. can also be powered from such a device.In another application, mugs, cups, or other containers with a receivercircuitry and means of heating or cooling the contents can be used incombination with the inductive charger or power supply to keep thecontents hot or cold. A dial or buttons on the cup or container can setthe temperature. The charging device or pad can also containrechargeable batteries that allow the device or pad to store energy andoperate in the absence of any external power if necessary.

Other applications of this technology include clothing, jackets, vests,etc. that have an integrated inductive charger or power supply such thata user can power or charge a device by simply placing it on or near apocket or an area where wireless inductive power is available. Thejacket or clothing can in turn be powered by solar cells, Fuel cells,batteries, or other forms of energy. It can also be powered by batteriesthat are recharged through solar cells sown onto the clothing or berecharged by placing or hanging the clothing item on a rack or locationwhere it is recharged wirelessly or inductively. By using inductivecharging, the user does not have to plug in devices into individualwires and connectors at the appropriate jacket pocket.

In some cases, it may be desirable to build the charger or power supplyor the secondary part (receiver for a charger or power supply) into theprotective case of another device. For example, many products existtoday that are after-market or optional items such as a skin or case fora music player, phone, PDA, or notebook computer. In one implementation,the case or skin can contain the electronics and the coil necessary toallow the device to be charged or charge other devices or both. Thecharger or power supply can be powered by the device it is attached toor can receive power from a separate source such as a solar cell, fuelcell, etc. that is integrated with the charger or power supply or inanother location and electrically connected to the charger or powersupply. For example, in a briefcase, while the charger or power supplyis inside the briefcase and can charge devices inside, the surface ofthe briefcase can have solar cells that power the charger or powersupply inside. The briefcase can also contain rechargeable batteriesthat store power generated by the solar cells and use them whennecessary to charge devices inside. Similarly, the charger or powersupply can be built on the outside or inside surface of the case andcharge devices placed on or near the surface.

It is also possible to provide a charger or power supply with modularcomponents that allow other capabilities to be added later orsimultaneously as an option. In one embodiment, an inductive chargingpad that contains a rechargeable battery can have a separate top surfacemodule or all around cover or skin that contains a solar cell array andsimultaneously electrically connect to the charger or power supply padto enable the battery internal to the unit to be charged without anyexternal power input. It is also possible to have the cover or theoutside skin to provide other capabilities such as communications, orsimply provide a different look or texture so that the pad fits in withthe user's taste or décor.

FIG. 61 shows an illustration of a kiosk that incorporates an inductivecharger or power supply unit in accordance with an embodiment. As shownin FIG. 61, the kiosk 390 includes a control screen 392 and an inductivecharging pad 394, to allow individuals to walk-up and purchase anoccasional charge for their mobile device. Currently, the usage model oftypical mobile user consists of charging their most essential device(phone, MP3 player, Bluetooth headset, etc.) during the night or at theoffice or car. In cases where the user is outside their environment fora long time such as traveling, this may not be possible. A variety ofpublic mobile device charging stations have appeared that allow the userto charge their device in a public setting by paying a fee. An inductiveor wire free public charging station or kiosk would allow the user toplace their mobile device that is ‘enabled’ (i.e. has the appropriatereceiver or components to allow it to receive power from the charger orpower supply) on or in the wire free or inductive charger or powersupply station and charge the device. The customer can pay for theservice or receive the service for free depending on the serviceproviders' approach. The payment can be cash, credit card, debit card,or other methods.

In accordance with an embodiment, a single pad with multiple stationscan charge multiplicity of devices simultaneously. The user may be askedto pay for the service before charging a device or the service may befor free. Alternatively, each charging station can be in a compartmentand the device is secured by a door that can only be opened through acode given to the device owner when charging starts or payment occurs.The door can also be secured by a combination lock or physical key.

Alternatively, the charging station or kiosk can be open and notphysically secure but when the user pays for the service, a code isissued. The user proceeds to place their device to be charged but whenthe charging ends or the user wants to pick up the device, the code mustbe entered first. If no code is entered, an alarm is sounded or thedevice is deactivated or some other warning occurs. In this way, a thiefor the wrong user can not remove the device without attracting attentionthat may act as a deterrent. A combination of the above techniques maybe used in implementing a public charging kiosk.

Since a typical charging process can take up to 30 minutes or more, itis possible to also synchronize data, download songs, movies, etc. intothe device during this time. Many of current mobile devices haveBluetooth or WiFi capability. Other communication protocols such asWiMax can increase the data rate further. By combining the charging andinformation transfer process, the service provider can charge foradditional services. In addition, if a camera is being charged and haswireless capability, it can download the pictures or movies to adesignated website or online storage area or be emailed to a designatedemail address while charging. In this way, a traveler can simultaneouslycharge a camera while downloading the contents of its memory to alocation with larger memory. This would enable the traveler to free uplimited memory space in their camera or other mobile device. Such aservice would enable devices that have limited or short range wirelesscommunication capabilities (such as mobile phones, MP3 players, cameras,etc.) to be able to connect to the internet and send or receive dataindirectly. It is important to recognize that without the chargingcapability, a device conducting such downloading or synchronizationthrough an intermediate device (Bluetooth to internet gateway forexample) often run out of power due to the length of time this takes. Inthis manner the charging capability of the kiosk enables a moreeffective operation.

Additional Applications—Inductive Charger Applications and Kiosk

With increased functionality in mobile devices, there is anever-increasing focus on maximizing the battery life. Currently, therate of increase of power usage continues to outpace new and improvedbattery technologies. Given the desire to minimize mobile device size,the battery power limitation has required some mobile devicemanufacturers to begin shipping mobile devices with several batteriesand a desktop charger to keep all of those batteries regularly charged.The user is sometimes expected to change the batteries for the deviceduring the day while using the device. Such a situation is not ideal andputs the burden on the user to carry multiple batteries, and to keepthose batteries charged.

Methods for extending the battery life in mobile devices, but which donot greatly increase the size and weight of the mobile device, areextremely useful for new power hungry enhanced multi-media mobiledevices. By way of example, one solution that has been proposed isdescribed in U.S. Pat. No. 6,184,654. However, such a technique andgeometry is incompatible with the variety of mobile devices andconnectors in use today, and requires the user to plug the device into aconnector inside the holster while fastening it to hold it securely.

Described herein is a system and method for extending the battery lifeof mobile devices by integrating a wireless charger into the case,carrier, or holster for the device. The system and method has theadvantage of keeping the size and weight of the mobile device low whileenabling the user to automatically recharge the device when placed inthe case thereby dramatically increasing the device run time.

In one embodiment, the case recharges the mobile device inductively, andcan itself be recharged by an inductive base charger. Variousembodiments including additional integrated functionality such as datastorage and communication in the case are also described herein.

FIG. 62 illustrates some common regular (non-charger) mobile phoneholders types, including a belt holder 1000 and case 1002.

Powering Mobile Devices and Inductive Charging Case

Mobile devices continue to converge and to combine multiple functionsand protocols into ever-smaller packages. While mobile TV, radio, highresolution cameras, GPS, etc. are becoming standard in many mobilephones, the power usage of the devices continues to rise. One solutionthat has been applied to several devices is the use of external batterypacks.

FIG. 63 illustrates various products for a music player, (e.g. an iPodor MP3 player) that include an external rechargeable battery pack.

As shown in, the external battery pack provides extra running power forthe device when it is plugged into the music device and clipped to itsback, by providing power through the battery pack's internal highercapacity batteries. However, this battery pack is expected to remainconnected to the device at all times and increases the size and weightof the device considerably. This is very undesirable from the customerperspective and inhibits mobility/use and adoption.

In accordance with embodiments of an embodiment, the battery power ofthe mobile device is extended by providing a holster, case, pouch, bag,wallet, or an equivalent holding, carrying, or storage device (which forconvenience are herein referred to as a “case”) for the mobile device(e.g. mobile phone, Bluetooth headset, camera, laptop, PDA, MP3 player,game player, etc.). The case can incorporate one or more rechargeablebatteries, and one or more inductive charger or power supplies. A mobiledevice can be ‘enabled’ to receive power inductively by providing areceiver (such as a coil, etc.), and circuitry integrated by themanufacturer, or by a battery with a built-in receiver, or by a plug-inunit to receive power, etc. A suitably enabled device can thus receivepower when placed in the case. In accordance with some embodiments, thecase can also include means of recognition of the device automaticallyby, for example, RFID, Felica, detection of coil from change in thecase's coil's induction, or by verification using proprietarytechniques, etc. In some embodiments, the system or coil can be enabledto turn on automatically as necessary and to begin charging the device.Alternatively, the case and/or coils can turn on when a device is placedin it by sensing the presence of a device through a magnetic,mechanical, or other form of switch. Alternatively, the case can includea mechanical or sensory switch that must be manually activated by a userto begin charging the device.

In accordance with some embodiments, the case can accommodate more thanone device. For example, the case can include a location for a Bluetoothheadset and a mobile phone. Either or both of these devices can beinductively charged by the case when placed inside the case. Thisenables the user to have a simple way to carry both parts or devicestogether, and to extend the battery capacity of both without needingthem to be any larger, thus providing great advantages for the consumer.

In accordance with an embodiment, the batteries inside the inductivecharger case can themselves be charged by either a regular charger/powersupply, or through another inductive charger or power supply. Forexample, a desktop inductive charger can charge the inductive chargercase, and simultaneously charge the mobile devices (mobile phone,Bluetooth headset, camera, etc.) or battery. Alternatively, the desktopcharger or power supply or base can be designed so that it can alsocharge the mobile device directly when the device is placed on it(without any case present). As described above, the inductive case canalso be designed so that it will charge its internal batteries, and thedevices inside, when it is connected to a regular power supply/charger.

Some embodiments of the case can include data storage, communication orother capabilities (for example, GPS, WiFi, etc.).

FIG. 64 illustrates a multi-function device that includes a hard drive,rechargeable battery, Bluetooth, and WiFi connectivity.

Typical multi-function devices such as that shown in FIG. 64 are of thesize of a credit card and about 10 mm in thickness. The multifunctiondevice allows a mobile phone user to store the majority of their digitaldata (pictures, movies, music, etc.), and to have that data availablewirelessly on their mobile devices. The mobile phone and multifunctiondevice can also connect wirelessly to a computer or laptop, for downloador upload of information.

In accordance with an embodiment, a multifunction device such as thatshown in FIG. 3 can be integrated into the case, and can have a wirelesscharger or power supply built into it. Once a mobile device is placedinto the case or on the modified multifunction device, it can establishcommunication, and/or can be charged simultaneously. Since a typicalmultifunction device already has internal rechargeable batteries, thesame batteries can be used to power the charger for the mobile device.The multifunction device case can also be charged wirelessly (using aninductive charger or power supply pad or similar device), or throughconventional means.

In other embodiments, the wireless charger or power supply case can beintegrated into a compartment in a briefcase, handbag, backpack,carrier, clothing, automobile, airplane, or other transport vehicle,etc. Some of these are applications are described in further detail incopending U.S. Patent Application titled “INDUCTIVE POWER SOURCE ANDCHARGING SYSTEM”; application Ser. No. 11/669,113, incorporated hereinby reference.

FIG. 65 illustrates a system for use with a charger or power supply caseto inductively power or charge a mobile device. As shown therein, aninductive charger or power supply base or pad charges a case, holster,or other small, portable charger that in turn can charge or power amobile device or battery placed in proximity to it. The second part(charger case) can be a stand-alone device or be integrated into anotherdevice, as in the case of the multifunction device example describedabove. In other embodiments, the charger or power supply case can becharged or powered through a conventional, wired charger or powersupply. In accordance with an embodiment, the system comprises:

Inductive Charger or Power Supply Base: In accordance with anembodiment, this part can be a stand-alone charger or power supply ordesktop charger or power supply that comprises a Field Effect Transistor(FET) that periodically turns the current through a coil on and off. Inone embodiment, for a typical 9 turn PCB coil with 1″ diameter, a drivefrequency of 1-2 MHz is ideal, and the power transfer efficiency isincreased when a capacitor of appropriate value is placed in parallelwith the FET. When the circuit is driven at a resonant frequency, theamount of current through the FET can vary greatly by proximity ofanother coil (L2) to L1. To allow the system to operate automatically, acurrent sensing system can be used to sense the secondary (L2) being inclose proximity to the primary (L1). In other embodiments, a separatecircuit for positive identification of a device to be charged being inproximity can be integrated. These can include wireless identificationsystems such as RFID, Felica, Bluetooth, WiFi, WiMax, etc. In anotherembodiment, the system of the charger or power supply case can bedesigned so that a chip in the charger or power supply case (near L2)senses an input voltage and modulates the current through L2 in apre-programmed manner. This results in a modulation in the current in L1that can be sensed with the current sensor and positively identifies thecharger or power supply case and initiates power transfer and operationif the pattern matches a pre-stored pattern for verification. In someembodiments, the inductive charger or power supply base can have theshape of a formed piece that the inductive case would fit into, or a padfor placement of the inductive case and/or mobile devices or both.

Inductive case: In accordance with an embodiment, the case has means forreceipt of power inductively (from the charger or power supply base) andcharging another device (or number of devices) inductively.Alternatively, it may be possible for the case to be designed so that itoperates by being charged or powered directly by a wired powersupply/charger. The case has a receiver part that is connected to abattery charger circuit that charges one or more internal batteries andsimultaneously, can also operate the circuitry in the charger or powersupply case to charge a nearby mobile device or battery. The case hascharger or power supply circuitry similar to the charger or power supplybase that can be powered by its internal battery or the power from thecharger or power supply base. The case can in turn recognize a nearbymobile device automatically or through mechanical or other means asdescribed earlier and commence charging when a mobile device is placedin or near the case/holster. In another embodiment, the charger or powersupply case may contain two or more charger or power supply sections sothat several devices in the case (e.g. mobile phone and a headset) canbe charged simultaneously. As described earlier, the circuitry/functionsdescribed here can be integrated into a device that also extends thefunctionality to storage, WiFi or Bluetooth connectivity, etc. In oneembodiment, the batteries in the charger or power supply case areidentical to the batteries used in the mobile device and are removable.In this case, the user may exchange the batteries between the charger orpower supply case and the mobile device (such as a mobile phone) in anemergency to allow quick use of the mobile device without waiting forthe charging of the mobile device to occur. This can provide anadditional desirable feature for the user.

Mobile Device Receiver: In accordance with an embodiment, the mobilereceiver part comprises a coil and circuitry that can be eitherintegrated into a mobile device by the manufacturer (i.e. an OEM),integrated into a battery that can be swapped with the original batteryto enable a mobile device to receive power inductively, or provided as aplug in unit that plugs into the existing power jack of a device and hasthe coil and the circuitry to enable the device to receive powerinductively. Alternatively, the receiver can be built into a jacket orskin for a device that plugs into the device and allows the device tobecome ‘enabled’. Variations of these are described in further detail incopending U.S. Patent Application titled “INDUCTIVE POWER SOURCE ANDCHARGING SYSTEM”; application Ser. No. 11/669,113. The above-referencedpatent application also describes the use of attracting magnets placedat the center of an inductive charger or power supply's PCB coil, andthe center of the receive coil, to align and center the two partsconveniently. Such techniques can be used in the base to case coilalignment, or the case to mobile device alignment or both. In addition,the alignment can be achieved through visual or mechanical marks,indentation, or mechanical design of the parts to enable easy alignment.

Heat Reduction and Dissipation

In order to generate the magnetic field for an inductive charger and/orpower supply, a coil made of wires or printed on PCB is typically used.Such a coil can be in a simple way, modeled by an inductive andresistive element in series. The resistance of the coil can be estimatedby using the dimensions of the wire or PCB trace, its length, and theresistivity of the material used (such as copper). At higherfrequencies, the resistance increases due to the skin effect whereby theelectrical current travels near the surface of the wire or trace ratherthan throughout its cross section, thereby decreasing the wire's ortrace's effective cross section. In order to obtain reasonable inductivevalues, several turns of wire or PCB trace are necessary.

For example, in a PCB spiral coil of 1.25″diameter, about 10 turns arenecessary for a 1 micro Henry inductance value. To design a highefficiency inductive power transfer coil, the resistivity of the coilmust be minimized while the resulting induction is kept at desiredlevels. It must be noted that any heat generated at the coil willincrease the resistivity of the coil material in turn leading to higherheat generation and temperature increase. To avoid this positivefeedback for heat generation, the main methods for reduction oftemperature at the inductive coil include reduction of heat generatedand dispersal of heat away from the coil.

In addition, electronic devices generally need to satisfy regulatory andsafety requirements which include the requirement not to interfere withthe operation of nearby devices. For an inductive charger and/or powersupply that creates a time varying magnetic field to transfer energy toa receiver, care must be taken to keep the level of interference tobelow allowed limits.

In general, the magnetic created by a small coil (˜1″ diameter) ofseveral turns when it is driven by an electrical voltage at around 1MHz, does not radiate more than several mm beyond the coil and isconfined to the near field. To reduce the effect of such radiation (forexample, as provided in Near Field Power™ radiation devices) at higherfrequencies, which are of bigger concern for most devices, the drivingvoltage of the circuit must be made to have weaker higher harmonics.

Another concern for generation of Electromagnetic Interference (EMI) isthe electronic circuitry and switching Field Effect Transistor (FET)incorporated in the circuit. Such components can be additional noisesources. Described herein are some ways of reducing the effect of aboveEMI sources.

Another important factor in efficient operation of an inductivecharger/power supply is the alignment of the charger/power supply coiland the receiver coil in the device to be charged/powered. Variousmethods of alignment of the coils using magnets have been described inprior applications. In addition, also described are the use of movingcoils and other methods by which several coils or clusters of coils canbe used to provide position tolerance between the coils for efficientpower transfer.

In accordance with an embodiment, to reduce the temperature increase atthe inductive coil, several methods can be used.

In accordance with an embodiment, the coil can be optimized by using theminimum number of turns necessary thereby decreasing the length andresistance of the coil. The diameter, thickness, or width of the wire orPCB trace can be optimized to provide optimum resistance.

For coils such as PCB coils discussed above, the magnetic field createdis strong inside the coil, and drops very rapidly as the radial distanceto the center of the coil exceeds the radius of the coil. Thisdependence can be verified using electromagnetic modeling (such asdescribed in Xun Liu; Hui, S. Y., Optimal Design of a Hybrid WindingStructure for Planar Contactless Battery Charging Platform, IEEETransactions on Power Electronics, Volume 23, Issue 1, January 2008Page(s): 455-463), and also by experimental means. The heat generated atthe coil can be dispersed away from the coil by use of high heatconductivity PCB substrates or material for the coils. Since themagnetic field is minimal in the area outside the coil, use of highconductivity metal layers will not have a large effect on the field andwill not create undesirable eddy currents. Therefore, the surface of thearea surrounding the coil can be designed to have metal or othermaterial that have high heat conductivity and remove the generated heatrapidly.

FIG. 66 is an illustration that shows a geometry for an arrangement 1030in which the area surrounding a PCB coil is designed to have metal onthe top, bottom or another layer of the PCB. As shown in FIG. 66, thearea surrounding a PCB coil is designed to have metal on the top, bottomor another layer of the PCB. The metal pattern can be incorporated atthe same layer as the coil or a separate PCB layer. This metal layer canbe continuous or have a gap in one area to avoid generation of eddycurrents due to circulating electrons due to magnetic fields generatedby the coil. In a typical PCB, the coil and the metal layer are made ofcopper. In this manner, any heat generated at the coil is dispersedlaterally rapidly and thus does not result in large temperatureincrease. In accordance with an embodiment, such a PCB can be itself thetop layer of an inductive charger in which case, any heat carried awayby the metal layer can be additionally evaporated to the surroundingenvironment. Alternatively, the heat can be further dispersed by removalto another area or surface or use of elements such as fins or slits.Similarly, the receiver coil and the circuitry for receiving power thatis integrated into a device, battery, outside carrier of an electronicsdevice, etc. can have a similar geometry to enable dispersal of heatgenerated.

In accordance with an embodiment, for typical applications with a PCB,the metal layer can be made from copper material similar to that of thePCB coil itself, and it is desired to have sufficient thickness toprovide a low thermal conductivity path for the heat. For example, acopper layer of several microns or even 10s of micrometers can be used.

Any such high thermal conductivity or metal layer may begin at the edgeof the PCB coil or with a gap to the PCB coil. Since the layer is notcovering the PCB coil, it may not cause eddy current loss in the layer.In those instances that eddy currents are generated, a gap in the metallayer as shown in FIG. 66 can be used to reduce the effect ofcirculating currents, and reduce the resultant heating and power draw.In accordance with an embodiment a metal layer can be used on top of thecoil (with a thin non-conducting layer or dielectric in between) if itsthickness is small. For example, in previous applications as referencedabove, the use of a thin layer of metal (several micrometers) on top ofa PCB coil was described to act as an EMI shield for high frequencieswhile transmitting low (around 1 MHz and below) frequencies of theinductive charger. Such a layer may also be used in addition to themetal layer surrounding the coil to facilitate heat dispersal.

FIG. 67 is an illustration that shows, in a multi-charger or powersupply where multiple coils are used, such a high heat conductivitylayer 1040 may be repeated around each coil or cover all areas betweenthe multiple coils.

FIG. 68 is an illustration that shows a similar method may be used forheat removal from wound coils of other shape and type 1050, 1056. Inaccordance with the geometry of this embodiment, to facilitate heatremoval from a coil that may be a wound coil around a core, the coil maybe attached to a high heat conductivity layer or a metal layer. In thecase of a metal layer, such a layer can be designed to be in the areasurrounding the outside of the coil to avoid interference with the fieldgenerated inside the coil. Similarly, to avoid eddy currents, the metallayer or the core of the wound coil or both can have a gap ordiscontinuous portion to reduce circulating currents.

In above examples, a metal or high heat conductivity layer has beenshown. FIG. 69 shows an illustration of an embodiment 1060 in which thelayer can be patterned to provide heat conductivity channels rather thana continuous layer if needed.

In accordance with any of the above geometries, additional means of heatremoval such as use of fins, fans, additional surfaces, heat pipes,thermal grease, thermally conductive epoxies, etc. can be incorporatedto facilitate heat removal. In addition, it is possible to incorporateheat conducting layers, such as ceramics or polymers can be incorporatedbelow or above the main PCB to help in heat removal.

In the above discussion, round shape coils are generally shown. It willbe evident that the techniques described herein are applicable to coilsof other shape or multiple coils in a cluster or separated to power orcharge separate devices. In many instances, the increase of thetemperature at the center of a PCB coil is largest. To remove this heat,in accordance with an embodiment the surface of the charger or a layerbehind the coil that contains high heat conductivity material can beused to disperse the generated heat laterally. An example of such alayer is ceramic material. High alumina ceramics can provide high heatconductivity and low electrical conductivity, which characteristics areimportant for this application.

Reduction of EMI from Inductive Charger and/or Power Supply

An advantage of the metal layers discussed above is that any EMIgenerated inside the inductive charger or power supply will be greatlyshielded from the outside and will be attenuated outside the charger orpower supply device by the metal layer.

Additionally, in the above geometries, the metal layer on the top layercan be made to contact electrically to other metal layers on the sideand/or bottom of the charger and/or power supply, thereby forming a boxor other enclosed shape where only the coil is not covered by metal.Such an enclosure will greatly attenuate EMI from the switchingelectronics or other parts in the charger. To reduce the effect of thepotential eddy currents generated in the metal box due to the magneticfield, in some embodiments it is useful to eliminate use of metaldirectly below the coil area where magnetic fields may exist. Inaddition, to avoid generation of eddy currents in the walls of the metalbox or similar outside surface, the wall can be cut in one or morelocation so that a continuous metal circuit or ring is not formed, anddoes not allow the electrons to circle unimpeded. This gap can be filledwith a non-conductive material to provide rigidity.

In the geometries shown above, it is possible to use a PCB whereby thecoil is formed in one area and the electronics is on the same PCB. Inaccordance with an embodiment, to provide shielding and heat dissipationdiscussed above, the metal layer around the coil may be in a layer ontop (closer to the outside surface) of the PCB. For example, the coilmay be formed on the top layer of the PCB along with the heatdissipation and/or EMI shield layer and the PCB electronic componentsmay be on the bottom layer of the PCB. Alternatively, the metal layercan be in a separate layer in the middle or even the bottom layer withthe PCB electronic components. However, the EMI shielding effects fromthe electronics components will be reduced if the metal layer surroundsthe electronics area and does not provide an electrical barrier directlyabove it.

FIG. 70 shows an illustration of the electronics for the PCB coilinductive charger and/or power supply or the inductive receiver asfabricated on the same PCB as the coil in accordance with variousembodiments 1070, 1076. The electronics in this case may be at thebottom layer, while the coil and the metal layer surrounding the coilare on the top layer and shield any electronic noise generated by theelectronics from the outside.

Any of the shapes and geometries discussed above are equally appropriatefor incorporation into the charger and/or power supply coil or thereceiver coil and for dispersal of heat and reduction of EMI from adevice to be charged/powered inductively as well as the coil in thecharger/power supply itself.

Magnetic Alignment of Coils

In accordance with an embodiment, to enable efficient power transfer inan inductive charger and/or power supply, the coils in the chargerand/or power supply and the receiver must generally be aligned with onanother.

FIG. 71 shows an embodiment 1080 in which magnets placed at the centerof a stationary coil or a moving, floating charger and/or power supplycoil and the receiver coil can provide a method for alignment of thecoils and to achieve this result.

A problem with this method is that, since the magnetic material iscomposed of electrically conductive material, eddy currents can begenerated when the coils are operated to generate a time-varyingmagnetic field. This can cause lost power, and can also cause heating inthe magnets which is not beneficial.

To address this problem, FIG. 72 illustrates an embodiment 1090 in whichtwo or more magnets that do not cross the center of the coil are used.This geometry reduces the eddy currents created greatly. In accordancewith an embodiment, the system can use an alternative magnet geometrythat provides a simple and inexpensive method for alignment of coils. Inaddition, this method provides for a considerable amount of alignmenttolerance when placing a device on the charger and/or power supply.

To provide alignment magnets that will not draw current due to eddycurrents created in them when a magnetic field is applied, in accordancewith an embodiment the magnets are placed outside the PCB coil area.

FIG. 73 is an illustration of two embodiments 1094, 1098 that shows howthe magnets may be placed outside the PCB coil area. The magnet shown inFIG. 73 comprises a ring that surrounds the coil or overlaps each coilsuch that little effect on eddy current generation or loss is created.If any eddy current effects are observed, then in accordance with anembodiment gaps can be inserted in the magnet ring by cutting aftermanufacture or by inserting this separation during manufacture. In thismanner the eddy currents can be significantly reduced or eliminated. Themagnet in the case shown is magnetized perpendicular to the surface ofthe ring. By attaching one magnet to around the charger and/or powersupply coil and another magnet with opposing polarity to the receivercoil, the two coils can easily be aligned with minimal effort by theuser.

In addition, the use of a ring has the advantage of allowing circularlysymmetric operation so that the two coils can be rotated with respect toeach other with no effect on charger/power supply operation orefficiency.

A typical geometry for the charger/power supply can comprise the PCBshown in FIG. 8 such that the coil can be fabricated on the top surfaceof the PCB, and the magnetic ring is attached to the bottom side of thePCB where the electronics may be located. A similar receiver can have amagnet attached with opposing polarity so that when the receiver isbrought close to the charger/power supply, the two magnets can attractand pull the coils into alignment. With this geometry, the magneticfield of the coils create attraction and alignment as long as the coilshave any overlap.

For example for coils of 1.25″ outside diameter and using ring magnetsof 1.25″ inner diameter, as long as the centers of the coils are lessthan 1.25″ away laterally, the coils can be brought into alignment whenthe two magnets are vertically (distance in the axis perpendicular tothe plane of the coil) brought close enough to allow the magnetic fieldsto sense each other. Thus in this case, if the user brings the center ofthe receiver coil to be within a circle of 1.25″ radius of the center ofthe charger/power supply coil, the coils can attract and provideautomatic alignment of the parts.

For most applications, this amount of alignment tolerance is sufficient.By using marks to outline the location for the coil on the surface, thisdegree of tolerance allows the user to place a device or batteryincorporating the receiver coil very easily into the right location.

Examples of magnets that can be used include those manufactured fromvarious magnetic material such as Neodymium Iron Boron, Samarium Cobalt,AlNiCo, ceramics, bonded magnetic material, etc. The magnetic strengthcan be designed to provide alignment or secure attachment without beingtoo strong or difficult for separation.

Alternatively, the coils can be manufactured on the lower surface closeto the magnet and the electronics or can be manufactured on anotherlayer in between. Various geometries are possible. In any case, themagnets can be used to align the two coils for optimum operation.

In above description, ring shaped magnets are described. However, inmany cases, size and spacing requirements may require use of a differentgeometry.

FIG. 74 shows an embodiment 1100 in which magnetic arc shaped partsaround a circular coil are used. This case may be combined with thematching magnet on the other coil having the same shape or a ring shapesimilar to FIG. 73. For example, in a mobile battery application wherethe battery with an integrated inductive receiver is charged byplacement on an inductive charger pad, the size of the coil determinesthe received power and may require the width of the battery to be equalor similar to the receiver coil. To allow attachment of alignmentmagnets, two arcs as shown in FIG. 9 can be attached to the coil. Inthis case, the magnets can be placed in between the battery and the coilPCB to allow the coil to be on the top surface and therefore closest tothe charger coil. The matching magnet in the charger can be a ring or asimilar set of arcs or another shape or size to facilitate alignment. Ifa ring is used behind the charger coil, then central symmetry betweenthe two parts is retained and the parts can be rotated with respect toeach other while keeping alignment for optimum operation.

Other geometries are possible. For example, FIG. 75 illustratesembodiments 1120, 1126 in which the use of bar magnets on or around thecoil is shown. Such a geometry does not have the symmetry offered by aring magnet. However, this may be useful if only one dimension ofalignment insensitivity is desired.

In any of the above geometries, use of two magnets with opposingpolarity to attract each other is described. However, in accordance withsome embodiments it is preferable for one of the parts to benon-magnetized. This may be advantageous in cases where it is notdesirable for the mobile device to attract metallic parts when not beingcharged or powered by the inductive charger/power supply. An example maybe a mobile phone where it is not desirable for the phone to attractmetallic objects during normal use. In this case, the charger and/orpower supply can contain a magnetized part and the other matching partin the mobile device/battery, can be made of appropriate magneticmaterial but not magnetized. For example, the charger/power supply maycontain a magnetized ring as described above and a mobile phone can havea matching ring or arc made of magnetic material but not magnetized.

In addition, it is possible for the charger and/or power supply magnetto be activated electrically and be normally non-magnetized. Forexample, a wire winding or PCB trace is placed around the perimeter ofthe power transfer coil and powered to create a DC magnetic field foralignment of the two coils for power transfer/charging. In this way,neither of the two alignment parts need to be normally magnetized andtherefore eliminate any concerns regarding unintended attraction ofmetallic objects or effects on magnetically sensitive parts such ascredit cards, etc. The generated magnetic field can be furtherstrengthened by using a non-magnetized magnetic material on or near thealignment trace area.

As an example, a circular path around the main charger/power supply PCBcoil can be powered by a DC current periodically or when a user desiresto charge or power a mobile device. This can be done by the user or canalso be activated automatically by a sensor that senses the approach ofan appropriate device to be charged or powered through RF, optical,magnetic, or other methods. Once the magnetic field (such as a ringpattern as described above), is generated it will attract and align amagnetic metal part or magnet of appropriate shape in the mobile deviceor battery into the correct alignment and placement and help the userplace the mobile device in the correct position. Once the device isplaced in the right location, the DC magnetic field may no longer benecessary and can be shut down or reduced to save power. Thus only for avery brief period this alignment magnet may be needed. During othertimes, neither the charger and/or power supply or the mobile device canbe designed to have any magnetic field around them or contain weakermagnets.

The use of magnets as described above is especially useful for caseswhere movement between the power supply and/or charger and the device orbattery to be charged or powered may occur. As an example, in anautomobile environment, it is desirable to keep a mobile device such asa phone from moving during charging. Thus the use of the magnetsdescribed above, in addition to the above benefits, can enable use inmoving environments. In addition, in some cases, it may be beneficial tohave the charger and/or power supply in a position that is nothorizontal. For example, a charger can be installed vertically. In thiscase, the magnets can be designed to be strong enough to hold the mobiledevice or battery in place vertically during the charging or poweringprocess.

In any of the above geometries, if any additional eddy currents aregenerated as a result of the presence of the magnets, the effect can beminimized by fabricating the coil from low electrical conductivitymaterials or ceramics, layering the magnet into thin sheets to increaseresistivity, using bonded material in an epoxy matrix, roughing thesurface, cutting gaps in the material to reduce circular motion ofelectrons, or other common techniques to increase the resistivity. Themagnet can also be manufactured from segments that are not electricallyconnected to prevent electrons to be able to travel around a circularpath. For example, the ring magnet can be manufactured, formed orattached to the coils from two or four ring arcs that are notelectrically in contact or attached to each other, using anon-conducting epoxy to form a full ring, or parts of a ring.

In addition, the coils shown above are generally circular. However, themethods and discussion above can be applied to coils of any shape andsize as well as an array or cluster of coils and can provide inperformance of any size and type of coil.

The foregoing description of an embodiment has been provided for thepurposes of illustration and description. It is not intended to beexhaustive or to limit an embodiment to the precise forms disclosed. Theembodiments were chosen and described in order to best explain theprinciples of an embodiment and its practical application, therebyenabling others skilled in the art to understand an embodiment forvarious embodiments and with various modifications that are suited tothe particular use contemplated. It is intended that the scope of anembodiment be defined by the following claims and their equivalence.

Some aspects of an embodiment may be conveniently implemented using aconventional general purpose or a specialized digital computer,microprocessor, or electronic circuitry programmed according to theteachings of the present disclosure. Appropriate software coding canreadily be prepared by skilled programmers and circuit designers basedon the teachings of the present disclosure, as will be apparent to thoseskilled in the art.

In some embodiments, an embodiment includes a computer program productwhich is a storage medium (media) having instructions stored thereon/inwhich can be used to program a computer to perform any of the processesof an embodiment. The storage medium can include, but is not limited to,any type of disk including floppy disks, optical discs, DVD, CD-ROMs,microdrive, and magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs,DRAMs, VRAMs, flash memory devices, magnetic or optical cards,nanosystems (including molecular memory ICs), or any type of media ordevice suitable for storing instructions and/or data.

The foregoing description of an embodiment has been provided for thepurposes of illustration and description. It is not intended to beexhaustive or to limit an embodiment to the precise forms disclosed.Many modifications and variations will be apparent to the practitionerskilled in the art. Particularly, while the embodiments of the systemsand methods described above are described in the context of chargingpads, it will be evident that the system and methods may be used withother types of charger or power supplies. Similarly, while theembodiments described above are described in the context of chargingmobile devices, other types of devices can be used. The embodiments werechosen and described in order to best explain the principles of anembodiment and its practical application, thereby enabling othersskilled in the art to understand an embodiment for various embodimentsand with various modifications that are suited to the particular usecontemplated. It is intended that the scope of an embodiment be definedby the following claims and their equivalence.

What is claimed is:
 1. A system for improved efficiency and flexibilityin inductive charging, comprising: a base unit having one or moreprimary coils, wherein each primary coil is configured so that when acurrent is passed through it, a magnetic field is generated in adirection substantially perpendicular to the plane of the primary coil;one or more secondary coils or receivers associated with one or moremobile device; and one or more components within the base unit and/orthe mobile device, for improving efficiency and/or flexibility ininductive charging, wherein when the one or more mobile device is placedin proximity to the base unit, the perpendicular magnetic field is usedto inductively generate a current in the one or more secondary coils orreceivers associated therewith, to charge or power the device, andfurther wherein the base unit and/or mobile device periodically verifyor handshake the presence of a mobile device proximate the base unit,and thereafter control the operation of the primary coils asappropriate.
 2. The system of claim 1, wherein the receiver is acomponent of, or is attached to, a shell, case, or other cover of themobile device.
 3. The system of claim 1, wherein the base unit includesa plurality of layers of primary coils and/or a plurality of primarycoils arranged as a stack.
 4. The system of claim 1, wherein the baseunit and/or mobile device includes a microcontroller for use incontrolling charging or powering, including monitoring current flowand/or providing communication between the base unit and the mobiledevice.
 5. The system of claim 1, wherein the base unit and/or mobiledevice verify the authenticity, power requirements and/or othercharacteristics of the mobile device or a battery therein, prior tocharging or powering the device.
 6. The system of claim 1, wherein acircuitry associated with the base unit and/or mobile device uses zerovoltage switching to control the charging or powering of the mobiledevice.
 7. The system of claim 1, wherein the primary coil and/orsecondary coil have a thermal dissipation layer associated therewith fordissipating heat and/or reducing electromagnetic interference.
 8. Thesystem of claim 1, wherein the base unit is provided within anautomobile, for use in charging or powering one or more mobile deviceswithin the automobile, and/or the mobile device is an automobile thatcan be charged by a base unit.
 9. A method of providing improvedefficiency and flexibility in inductive charging, comprising the stepsof: providing a base unit having one or more primary coils, wherein eachprimary coil is configured so that when a current is passed through it,a magnetic field is generated in a direction substantially perpendicularto the plane of the primary coil, and wherein the base unit includes aplurality of layers of primary coils and/or a plurality of primary coilsarranged as a stack; providing one or more secondary coils or receiversassociated with one or more mobile devices; and providing one or morecomponents within the base unit and/or the mobile devices, for improvingefficiency and/or flexibility in inductive charging, wherein when theone or more mobile devices are placed in proximity to the base unit, theperpendicular magnetic field is used to inductively generate a currentin the one or more secondary coils or receivers associated therewith, tocharge or power the device.
 10. The method of claim 9, wherein thereceiver is a component of, or is attached to, a shell, case, or othercover of the mobile device.
 11. The method of claim 9, wherein the baseunit includes a plurality of primary coils, and further wherein eachprimary coil is driven by its own drive circuit to provide power to andselectively activate that coil as appropriate.
 12. The method of claim9, wherein the base unit and/or mobile device includes a microcontrollerfor use in controlling charging or powering, including monitoringcurrent flow and/or providing communication between the base unit andthe mobile device.
 13. The method of claim 9, wherein the base unitand/or mobile device verify the authenticity, power requirements and/orother characteristics of the mobile device or a battery therein, priorto charging or powering the device.
 14. The method of claim 9, whereinthe base unit and/or mobile device periodically verify or handshake thepresence of a mobile device proximate the base unit, and thereaftercontrol the operation of the primary coils as appropriate.
 15. Themethod of claim 9, wherein a circuitry associated with the base unitand/or mobile device uses zero voltage switching to control the chargingor powering of the mobile device.
 16. The method of claim 9, wherein theprimary coil and/or secondary coil have a thermal dissipation layerassociated therewith for dissipating heat and/or reducingelectromagnetic interference.
 17. The method of claim 9, wherein thebase unit is provided within an automobile, for use in charging orpowering one or more mobile devices within the automobile, and/or themobile device is an automobile that can be charged by a base unit.
 18. Asystem for improved efficiency and flexibility in inductive charging,comprising: a base unit having one or more primary coils, wherein eachprimary coil is configured so that when a current is passed through it,a magnetic field is generated in a direction substantially perpendicularto the plane of the primary coil; one or more secondary coils orreceivers associated with one or more mobile device; and one or morecomponents within the base unit and/or the mobile device, for improvingefficiency and/or flexibility in inductive charging, wherein when theone or more mobile device is placed in proximity to the base unit, theperpendicular magnetic field is used to inductively generate a currentin the one or more secondary coils or receivers associated therewith, tocharge or power the device, and the base unit and/or mobile deviceverify the authenticity, power requirements and/or other characteristicsof the mobile device or a battery therein, prior to charging or poweringthe device.
 19. The system of claim 18, wherein the receiver is acomponent of, or is attached to, a shell, case, or other cover of themobile device.
 20. The system of claim 1, wherein each primary coil isdriven by its own drive circuit to provide power to and selectivelyactivate that coil as appropriate.
 21. A system for improved efficiencyand flexibility in inductive charging, comprising: a base unit havingone or more primary coils, wherein each primary coil is configured sothat when a current is passed through it, a magnetic field is generatedin a direction substantially perpendicular to the plane of the primarycoil, and each primary coil is connected to a switch to provide power toand selectively activate that coil as appropriate; one or more secondarycoils or receivers associated with one or more mobile device; and one ormore components within the base unit and/or the mobile device, forimproving efficiency and/or flexibility in inductive charging, whereinwhen the one or more mobile device is placed in proximity to the baseunit, the perpendicular magnetic field is used to inductively generate acurrent in the one or more secondary coils or receivers associatedtherewith to charge or power the device.